I ran into the same problem on my solenoid. With all the add-ons that required 12v power, I found a temporary solution that has worked so well that it has become permanent.
I replaced the retaining nut that came on the solenoid with a coupling nut. After securing half of my connections, I tightened it down and bottomed a long set screw to the solenoid post. With 1/2"-3/4" protruding, I placed the remainder of my connections on set screw and anchored them with the original solenoid nut.

I developed a similar "feel" when I switched from stock to Ron Morris adjustable engine mounts. They are far more rigid than the factory offering and transmit a lot more of what you refer to as "feel" into the body structure. I eventually adjusted to it and don't even notice it any longer.

I run the exact setup you are inquiring about and have tried both 1/2" spacers. With the open spacer, I developed the annoying whistle you've probably read about. Holley tech told me to run the 4 hole and my 302 loves it.

MDL has a selection of Hurst shifter levers including one listed for 69-73 Mustangs. Might give you a place to start looking. They claim it is very similar in appearance to the production shifter, but fits the T5.

I had a similar problem on my '66. The cluster lights were initially dim and finally went totally out. After restoring my cluster with new lamps and 5v regulator, I ensured that the grounds were good but the problem persisted. I ultimately found dead spots in the dimmer function on the switch. Without removing it, I sprayed it with electrical contact cleaner and repeatedly rotated the knob back and forth to clean the contact. Problem solved!

If the motor is only getting up to 200*, you don't have a problem. I don't know where you have the fans coming on, but you should be fine running the A/C. I see only a small increase in temperature with my air running. I would definitely swap a 180* thermostat in it.

If what I see in the picture represents 6 months of leakage and you've never had to add coolant, I'd wipe it clean and forget about it for another six months!

My situation presented a similar problem. The EFI installation on my 302 required that I use the location usually reserved for the gauge sensor to be used for the EFI sensor. I had a thermostat housing with a tapped port, where I relocated my gauge sensor. During warm-up, the needle on the temp gauge will not move, but when the thermostat opens, the needle climbs very quickly to the operating temp. It's a good visual indication that the thermostat is working properly. I found that the temp gauge readings were virtually unaffected by the change.

I can't address some of the specific component issues you might encounter (i.e. steering gear or vert structure, but i can offer my impressions on the JBA fitment in general. My JBA system is installed in a '66 fastback with a 302, Edelbrock heads and T5 (Z-bar operated). Like you, I am running the Ron Morris mounts, which are necessary with these headers. I too found my engine crowding the driver's side, but the adjustable mounts corrected the alignment issue. Once positioned, I had no clearance issues in the engine compartment or anywhere else in the system, including H-pipe, mufflers or tailpipes (GT style).
I can tell you that the 1 5/8" primary tubes make it impossible to use locking header bolts. I had to grind a box end wrench to fit the tight clearance. 12pt. bolts would easily resolve this issue.
Changing plugs on the drivers side is horrible. Again, I had to make a special tool to remove the #8 plug. A conventional plug wrench/socket does not fit. In all fairness, I do have to deal with a power brake booster, which limits access.
Despite the drawbacks, they do fit without having to "dimple" anything. The quality of the ceramic coating and stainless steel headers is excellent.
I hope someone else can address the potential clearance issues associated with the convertible structure, steering gear and cable clutch linkage.

 

These are the paints I prefer and have used with great success. The Seymour lacquer is available at NPD. I do start with an etching primer on bare metal parts and use SEM standard primer (not high-build) on textured parts.

In the process of installing Sniper EFI, I elected to install sub-frame connectors and run the fuel lines along side (like MS suggested). I relocated them to the passenger side,which is a much easier route. I did have to route them through the tunnel support, but the installation ended up very clean.

The hard lines for the heater sounds great! I was assuming that the tensioner would be something like you describe. Make sure to post more pictures as you complete those items.

I would suggest replacing the entire set at one time. I tried to replace only the letters I needed and found that the face angle of the letters is slightly different from the OE letters, which causes them to pick up the light just different enough that you can easily pick out the replacements.