the pedal assembly on the left is from a 1971 Duster 225 3spd same as 318 .The one on the right 1971 duster 340 4spd. Note the different springs and pin to pin spread. The spring on the 340 is so heavy they added a brace.The later pedals with all 5 1/4 pin to pin and small spring Have a different brake pedal. The bar is turned sidways for impact protection. That is 73 and later. The early cars did have different different assemblies. and if not used with the correct components. will cause engagement and disingagment problems . Those of you who think there trans doesn't shift properly this is more than likely the culpret. I have alot of assemblies from different years. They changed alot more than this on early and later 4 spd. cars but this is what alot of concern is now. Hope this answers anyones questions as every other person has a different opinion. Mopar muscle ran a tech artical on this. They show you how to modify your pin to pin so it will work properly with a 10.5 clutch assembly. If needed I can scan it in and post it. If you have the small spring a diaphram will work without removing it if you keep the smaller spread. But put some ponies in front of it and tires behind it and let me know how it works then. Diaphram clutch No spring with large spread. Borg&Beck finger clutch large spring with large spread. Small spread will get you by but you will have problems with premature wear on the bearing or clutch. And disingagement when using the correct fork.