What do I gain by going to 'performance' front end parts?

Agree that intended use of the car ought to dictate choice of poly or rubber. Have had no squeaks with PST.

Anything you do to replace 40 yr old rubber in the front end is going to make things better. Same for replacing shocks. Strongly recommend a gas charged shock.

Front and rear sway bars are good. IMHO the factory LCAs with sway bar tabs are the way to go. Aftermarket tabs are too wimpy. An exception is an aftermarket LCA with tabs (but that's a few $s more).

Low profile tires are good, too. Go too low with the crappy streets here at the Edge of the World and you're going to bend a rim. I've found 60 series to be a good trade-off.

I have done all of the above to both cars and made them much more pleasant to drive. The most dramatic change I have made is to change the front end settings.

.5 degrees negative camber
1/16" toe-in
as much caster as posible up to +4º

The most I could get out either car was +2.5º. Still the turn-in difference was stunning. If you like it, thank AutoXCuda, he's da front-end guy.