I know this thread is old as the hills, but was wondering if you ever found any use of the EX-309.
A few of us are working on the 745/751 projects dealing with the ram board. Yes we know you can purchase the replacement ram boards that do not fail but this is an experiment we are working on.

I really like the old 745 style radios. Looking for modern ways to interface with the original ram board. There was a few programmers designed that would do this via LPT port years ago.