I used a kit from cvfracing.com for my 351W. I think they have kis for the 351C, too. Good quality, good prices, keeps the v-belt, etc. Overall it was a good buy.
1968 C Code Coupe - Getting a 289 and AOD - ON HOLD
1968 C Code Fastback - Getting a 351W and Tremec TKO 5 Speed - WORK IN PROGRESS!