The 351W and 351C use the small block bellhousing bolt pattern. The 351M and 400 use the big block bolt pattern.
The C4 auto trans
, which has a separate bell, can be used, but you'll probably have to go with an aftermarket bell for the big block pattern. The C4 has two different designs. One is a case fill, as used on Mustangs. The bell uses the trans
pump bolts to secure it to the housing and the dipstick is in the trans
housing. A 157 tooth flexplate and a converter with a 10 1/2" bolt pattern is used on vintage Mustangs.
The other is a pan fill, the dipstick is in the oil pan and it has separate bolts to secure the bell to the housing. This is a stronger and larger unit and was used in full sized cars and trucks. The flexplate is a 164 tooth and the converter has an 11 1/2" bolt pattern. The bells are not interchangable between the two designs.
Case fill bells with can be found that use both the large and small F/P and converter. The bell is deeper with the larger F/P and converter, though. The pan fill only uses the larger ones. You will have to consult the aftermarket as to which type C4 is used with the big block pattern.
The C6 has a one piece housing and is available in big and small block bolt patterns.
1982 and up 302/5.0 engines only, use a 50 oz imbalance. A Mustang 157T F/P with 50 oz and 10 1/2" bolt pattern is an aftermarket piece since no C4s with this imbalance factor were factory installed on these later engines. All of the other engines use a 28oz imbalance F/P throughout.