1975 12a in a 1979 RX-7?
 

Should I even consider putting a 75 12a into a 1979 RX-7? I'm talking about only the 'shortblock'. No accessories. Is there any difference in the two years?

Very Simple Swap!

There are some differences. You'll have to fill the ACV port (right below the primary intake ports) with quicksteel or something like devcon to prevent an exhaust leak under the manifiold, but only if you're using the '79 manifold. It lacks the casting to block the ACV port. Some people weld on some aluminum to the manifold and have it machined flat, which is an alternative. Or if you're lucky enough to have a '75 manifold kicking around, you can disregard everything I just said. :)

Thank you for the help!