If you are looking to do a Wagon, do try to get a late model with the one piece windshield. I built a '60 Wagon (split window) back in '81. Paid $600 for it and it had a Ford small block installed. A nice, little, 260 V8.
Why one piece? Even with a new gasket the windshield will want to leak.
Go ahead, ask me how I know...
If you find one local and would like an opinion,PM me and I will be more than glad to help! I may not know much, but I do know Willys.
You are correct about the 3a staying in production and I think it was in '56 when it made yet another appearance as the DJ-3a.
Size. Yup, the early CJ series were insanely small as they were still the same size as the MBs. One of the acceptance criteria for the MB, from the Army, was that with a guy on each corner, the vehicle had to be light enough to be picked up and carried out of a ditch. So, just how big can they be? I used to be 5'10" and do not fit well into the 2a I have. Sort of scrunched.
But, with the top off they are fun.