C4 to rebuild or not to rebuild?

Go with the agressive shift kit, you'll like it. What's not to like about stiffer shifts. IIRC, it's also easier on the clutches because it shifts faster. I had an early model C4 with a manual/automatic valve body that I really liked.

One thing to be away of is if it's an early or late model. You can tell by how many bolts are on the valve body. 8-bolt is early, 9-bolt is late. For some reason, with some (random) early model c4's, it won't hold 2nd gear with a manual/automatic valve body. It shifts to third on it's own. This may be the case also with the regular automatic valve body. It bugged me when racing because it would short shift 2nd all the time.

Now, I'm running an Art Carr C4 and it's great. It's got a reverse pattern manual valve body with a trans-brake. It spins in all shifts.