Zen, I'm running the 944 25.5mm torsion bars which were a good mix of track and street. It's on the tight side for street use but if you autox, hit track days, or frequently drive winding roads the setup is perfect. It never had any problem with my type 4 hanging off the back.
My old track/street setup
72 super
2L type 4
1303 lower control arms
modified 944 struts with kyb gr-2 inserts and eibach 12" 80lb/in. springs
86 944 n/a alu arms
86 944 club sport 25.5mm torsion bars
kyb gas-a-just shocks
6x16 fuchs w/ 205/55R16 potenza s-03
7x16 fuchs w/ 225/50R16 BFG GeForce T/A KD