I run a Centerforce diaphragm clutch in my '74 Dart Sport 360 4 speed.
It works awesome, and I removed the over center spring as well, (it tells you that in the instructions).
Just so you know, removing the spring with the pedals in the car is a PITA.
Stacking coins, washers, etc. in the spring didn't work for me.
I ended up cutting it out with a small die grinder with a cut off wheel.
Also, it's much easier with the pedal set out and the front seat removed........