SCM

I have read a great deal of information on the different head combinations on the Z's. Can anyone direct me or tell me where I can find out info on the engine blocks. I have just removed 2 motors and boxes from 81 and 82 Z,s and the numbers are different on the blocks. The 81 I think is a N45 or something of that nature, but the other on the 82 has F54.

Can anyone help?

SCM