I have a 1975 Old's with "J" type heads and I want to update them. I want to update using standard Old's parts and was wondering if I can simply transfer the valve train from my J-Heads to something like a C-head or a K-head. Is this possible or will I need to purchase new valves, etc. Perhaps someone could advise? Thanks...Max

 

should be ok although the older heads wont have hardened seats. the older a and b heads had a different type of rocker bridge that is hard to find

 

All BBO heads interchange. All except the rare D heads have chambers with about 80-ish CCs as cast (D heads are in the mid-70s) so CR will be the same. All G, GA, K, and KA, heads also have hardened seats in addition to the J heads, but this is only a thin induction hardening of the cast iron, not actual pressed in seats. This hardened layer will typically be removed if the valve seats are cut. Pay attention to valve size, as heads could have come with either big or small valves.