I have a 66 mustang with a 289 and a c4. I'm getting ready to rebuild the c4 but I'm getting alittle confused with the identifing marks. Thecasting number on the tail piece of the tranny is c7op-7a040, if i've done my research right this should be a 67 c4 off a fairlane/torino. Now where i'm getting confused with is the 5 bolt bell housing and 24 spline input shaft. I thought I had read that those should be on a 66 and earlier c4 where in 67 ford went to a 6 bolt bellhousing and a 26 spline input shaft. There is a metal tag on the tranny with PEA M1 and underneath that is C9APABM4. Another number is on the pump cover which is C6AP-7D027-C. It is an aluminium bellhousing with casting number RF-C5AP-7976-B. Any help with the numbers to find out what it really is would be great.