Ill be following your post.  I had a wonder also that I cant figure out.  Have the Rack and coil over suspension.  Steve69

In my recently updated opinion...you should endeavor to BECOME the Pro and NOT take it to an "pro".  We have a local guy who understands these old cars and will take the time to get them right...well, sort of.  I had him touch up the alignment on the Heap before we left for FWB and half way there it was making unusual noises.  Josh, Gary (RV6), Bob (RPM), and I did some parking lot investigation and discovered that the nuts on both UCA's were finger tight.  My fault for not following up but then should you have to follow up?  I guess one answer is YES YOU DO.  The other answer is DO IT YOURSELF.  I did ours years ago and it was fine for over 15K.  Then I lost my mind and got lazy. 
Buy a Longacre camber/caster gauge and learn to do it yourself.  For your slight left pull I think you should check that the caster is equal and try to get 2 to 5 degrees positive if you can. Then set up the camber to zero to 1/2 degree negative.  Use string touching the rear and front tires to set the toe to 1/16 to 1/8".

It's a PIA messing with shims and pulling and replacing the wheels but on a level floor you can get it very, very good and the time you spend will be well invested.

At least that's my opinion.

BB
 

I'll second what BB and Kelly are telling you.  Adjustable strut rods are a bit of a red herring.  The strut rod in these cars is really more to stabilize the LCA than it is to adjust caster, and they're definitely not a solution to try and true the chassis.  Consider how they work.  When you shorten the rod you are pulling the outer ends of the LCAs forward, but not in linear fashion.  The inner pivot points of the LCAs don't move, so as you adjust thw strut rods you are cocking the LCAs out of perpendicular to the centerline of the car.  I don't want to get into a treatise on chassis design, but you are also screwing with your Ackerman angle, which can make the car twitchy. 

GM cars (I know, I know) don't even have strut rods.  They use an LCA with two mounting points.  All caster/camber adjustment is made with shims between the UCA shaft and chassis.  That's how you really need to adjust your '65/'66 Mustang too.

If you need more caster a much better solution is to relocate the UCA mounting point a la the Shelby drop.  Everyone gets hung up on the lowering of the UCA mounting point, but part of the magic is also moving them rearward a bit.  That adds more static positive caster.  It also accomplishes that without touching the strut rods, and adding all the negatives that brings trying to adjust caster that way. 

I would also highly suggest picking up a caster/camber gauge and setting your own alignment.  My experience over the years with shops has been spotty at best.  Most have no idea how to set up an older car.  You can't go by the book specs, because they were designed for bias ply tires and will make the car handle like a death trap.  I've heard good things about the Longacre gauge.  I personally use a Fas Trax gauge.  Consider that a typical alignment costs around $90.  I think I have about $300 in my setup.  Pays for itself in short order, especially if you have a fleet like I do...

Bullet Bob wrote:

In my recently updated opinion...you should endeavor to BECOME the Pro and NOT take it to an "pro".  We have a local guy who understands these old cars and will take the time to get them right...well, sort of.  I had him touch up the alignment on the Heap before we left for FWB and half way there it was making unusual noises.  Josh, Gary (RV6), Bob (RPM), and I did some parking lot investigation and discovered that the nuts on both UCA's were finger tight.  My fault for not following up but then should you have to follow up?  I guess one answer is YES YOU DO.  The other answer is DO IT YOURSELF.  I did ours years ago and it was fine for over 15K.  Then I lost my mind and got lazy. 
Buy a Longacre camber/caster gauge and learn to do it yourself.  For your slight left pull I think you should check that the caster is equal and try to get 2 to 5 degrees positive if you can. Then set up the camber to zero to 1/2 degree negative.  Use string touching the rear and front tires to set the toe to 1/16 to 1/8".

It's a PIA messing with shims and pulling and replacing the wheels but on a level floor you can get it very, very good and the time you spend will be well invested.

At least that's my opinion.

BB
 

 
To some point I agree with BB as it applies to most things on our classic cars. However, at some point you have to be able to admit that what some guys are good at others are not. I don't know if it is my skill level or my patience but after devoting 3days to the driver side only I came to the conclusion that I lacked both. Thru a friend that successfully races a Factory Five Cobra I found a shop that did my alignment to my specs and have it driving beautifully. Just sayin. Moving on to the rear disc brake project.

I second TKO's comments with some additions.  When one sets the caster, the camber has to be in the ballpark, along with the toe.  In order to set the caster, one has to turn the wheels to the left and to the right the same amount, and check the bubble on the wheel, then make the necessary adjustments.  I used to teach the old Hunter string align setups common in the late 70's and 80's.  There are a few other things as well, such as locking all 4 wheel brakes, finding the wheel center in the gearbox and so on.

My adjustments would to be set the camber, get the toe reasonably straight, then check and set the caster, then review the camber and toe, they WILL change.  Once the caster is set, you can forget about it.  Toss in king pin inclination, scrub radius, bump steer, excess toe on turns, and one can have a real time setting up a front end. Many high end cars also use a spring loaded spreader bar to simulate the front wheel drag to properly set the front toe.

As for a car pulling one way or the other, caster will have the most effect, aside from tire pull.

66 coupe wrote:

I second TKO's comments with some additions.  When one sets the caster, the camber has to be in the ballpark, along with the toe.  In order to set the caster, one has to turn the wheels to the left and to the right the same amount, and check the bubble on the wheel, then make the necessary adjustments.  I used to teach the old Hunter string align setups common in the late 70's and 80's.  There are a few other things as well, such as locking all 4 wheel brakes, finding the wheel center in the gearbox and so on.

My adjustments would to be set the camber, get the toe reasonably straight, then check and set the caster, then review the camber and toe, they WILL change.  Once the caster is set, you can forget about it.  Toss in king pin inclination, scrub radius, bump steer, excess toe on turns, and one can have a real time setting up a front end. Many high end cars also use a spring loaded spreader bar to simulate the front wheel drag to properly set the front toe.

As for a car pulling one way or the other, caster will have the most effect, aside from tire pull.

That's absolutely true.  My assumption was you were setting alignment on a car where it was already reasonably close.  If you start off WAY out of whack though you do need to get it close enough to start, or you're back to chasing your tail.