I got your message via email this morning; not thru the mailbox here btw...
I am not sure as to what units will work on an RD-4. I may have a #41, still have some Be-Ge's for the rear.
Best to text me at (530)415-0504 or email [email protected] My Succeed account isn't set up properly.
Regards, Gee aka Juiceman.