Join Date: Sep 2010
Location: Palominas, Ariz Terr.
Re: Engine id 75 ranchero
Sounds like you do have the 4bbl Cleveland heads which are interchangeable with those of the 351M/400's.
A quick way to determine whether or not you have a C or an M is to measure the distance between the top two bell-housing bolts. If it's about 5 inches, you have the small-block pattern of a 351C. If it's about 7 inches you have the big block pattern used on the 351M's and 400's. If someone retro-fit a 351C into your truck, they would also have had to change the transmission to make it fit. ( or at least the bell-housing it it had an FMX tranny.)