I have a 69 Chevelle with a 454. It's finished except for a Saginaw 4 speed with an unknown clutch set up with 3:31 12 bolt rear. Someone grafted a Muncie shifter to fit a Saginaw and believe it or not, it shifts decently.
I want to put a Muncie in it's place. The clutch works good and there is little effort to push it in which I like.
Questions:
1. Replace with a Muncie and not touch the clutch?
2. Go ahead and replace clutch while it is down. If so, what clutch set up?
3. Look for wide ratio Muncie, (M-20 ?) because of 3:31
In other words, if this were your car what would you do in this area ?
Any info is appreciated.
Thanks.

M-20 built tight on the input as these don't survive with a lot of freeplay; new clutch to ensure all is well when you put it together (centerforce make good stuff)

It's a 454 so the gear ratio won't matter too much.
If you have the $$ go for a new auto gear M22W.
While the trans is out INSPECT the clutch, it may be near new and possibly a centerforce d/f by you description of the light pedal feel. If it is a d/f, it may last a long time yet.

Sorry but what's an auto gear m-20 ?
Thanks.