so i have 78 F-250 4X4 with a 400 and a C6. what i need to know is what engines (351M, 351C, 390 etc) will mate with the trans ( if i need a diff torque conv. ) and fit into the same engine mounts as the 400. any help would be greatly appreciated.

 

351/400M are the same motor and likely the same torque convertor for much of the line.

A 429/460 will practically bolt in, but it may need some accesories.

 

what about a 390? as for mounting, i ask only b/c i have easy acccess to one and its a good built motor.