The marine version of the FE cylinder head always has a "J" in the casting number, such as C7JE
That would be a 1967 vintage casting (the C=1960's) (the 7 = the year of the decade, meaning 1967) the "J" = marine, and the "E" signifies this is an "engine" part. Now beware.....you could have a cylinder head with the following number with an additional date code stamped in. The date code looks something like this "7A5".
You could have a cylinder head C5AE-F, with a date code of 7AF, which would mean it's a 427 head cast Jan 5, 1967. What looks clearly like a 1965 casting design, actually is a 1965 design, but it is date cast in 1967.
I've been told "any FE cylinder head will bolt to any FE block", and this may be true, however, by doing so you have no gaurantee that your valves won't hit the pistons, because piston height and crankshaft have to be taken into consideration too.
Is it possible to have a "stock" 427 marine motor with a 1965 designed casting, and a pair of 1967 heads? Yes, but not on a boat sold in 1966.
The 1965 block could have been put in storage, and stocked for marine use. It may not have been assembled until later, at which time it may have received heads from the 1967 run. With Ford, you really never know for sure, since most of the records are now gone forever, and many of the changes didn't seem to be recorded in the first place.
Will a set of 352 or 390 heads work on a marine 427??? This question has come up numerous times, and to my knowledge the answer is "yes". I believe the marine heads are "generic" in nature, with little to really designate them from marine or automotive use, other than brass plugs. If you go this route, it's up to you to verify the details, so please proceed carefully.
Here is my complete marine cylinder head photo documentation thread for reference purposes.
http://www.network54.com/Forum/message?forumid=424840&messageid=1121461942
Regards,
Paul