Gary is right.  If you want it perfect, send it to a shop that has a machine.  They will hand their newest least educated guy your distributor and he will toss a couple of new springs in it.

But, if you are less than perfect like most of us, you can get a performance curve in your distributor with about four possible combinations of springs.  Might not be perfect, but it will boost your performance.  The only difference is if your distributor has the RANGE of advance built into it to get the optimum performance.  That is where a distributor guy that knows his stuff can help out.

But, for basic performance gains (you said Pertonix, so I know top all-out performance is not your goal, but rather a dependable car that performs better than stock) you can buy this kit from Summit for under $6.00 that provides the springs to make your distributor have a faster curve than stock.  Varying one of the two springs with one of the existing springs, or both new,will let you set several different advance RATES.  They will not affect total possible advance.

Go to Summit Web site.  Search on FORD DISTRIBUTOR ADVANCE SPRINGS

 

Here's some info on the subject that I think is pretty useful:

http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html
http://www.460ford.com/forum/showthread.php?t=117504
http://www.bjsoffroad.com/forum/forum/customer-service/electrical-related-questions/2339-ignition-advance

One thing to remember is that Ford used a light and heavy spring for a good reason:  They result in a stepped advance.  This is accomplished by the light spring allowing some initial advance to occur because the heavy spring has a lot of play in its ends.  When that play gets taken up, the heavy spring then dominates, delaying the rest of the advance until higher rpms.  If you replace your springs with the two in the Mr Gasket kit (which are both the same), then you will not get that stepped advance.  That may be what you want, but you get to decide.

There's a lot of discussion about whether to use ported or manifold vacuum for the vacuum advance unit.  If the vacuum source comes from above the carburetor butterflies, then it's ported, meaning there will be little to no vacuum at idle.  Using manifold vacuum, results in high vacuum at idle.  Either can be useful, depending on how you want to set up your advance.  The additional advance at idle that manifold vacuum provides can make an engine with a lot of cam run smoother and cooler, but if not adjusted properly (too high), can make the engine stumble off idle when the advance drops as the mechanical advance just starts to take over.  In either case, you can measure the amount of vacuum you have at various conditions (e.g., idle, just off idle, etc.) with a vacuum gauge.  You can then use a vacuum pump on the vacuum advance unit to see when you'll get full advance, and make some preliminary adjustments.

Lastly, you have to have a way to measure all that advance.  Some people use dial back timing lights, but I don't, as they're expensive, I've read reports about them being inconsistent, and many don't work with CD ignitions.  I just use a timing tape and a 40 year old timing light. 
 

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