When modding a second gen TA there are a few things that I think should be considered:
1. As mentioned above, solid body mounts and SFC's. I went with a lowered Camaro mount which required slight alteration to the air cleaner base (since the motor is chassis mounted and the shaker is protruding). Also, the front indicators need an extension to lower them since they are mounted on the bumper (chassis).
2. The TA's appear higher in stance than Camaros since they have a different, rounder shaped wheel opening. I think they look best with at least a 1-2" drop. This is most easily accomplished with drop springs. Any additional drop will seriously affect ride/performance unless going to measures such as I mentioned above. They are also able to take a slightly larger wheel.
3. IMHO No mod should be performed that prevents the shaker from being motor mounted. Go with a 455 or whatever you like, but aftermarket intakes are often too tall to fit under a shaker. There are other means to achieve HP numbers. Shaker hoods are what defines the TA and differentiates it from it's second gen cousin (Along with the air extractors and spoilers).
Suspension performance is way above average for the period, nothing major needs to be done. Besides the subframe connectors I would add poly bushings and 4 wheel disc upgrades. Also some traction device is nice to avoid squat, wheel hop. I would recommend those with j-bolts that replace the bottom perch and factory u-bolt/t-bolt setup.
BTW, here's my 79 TA project: