Wheelbase:
81” pre 1972
83.5” 72-83
76-83 cj5 frames are fully boxed, just like the cj7 & cj8.
CJ5s don’t like Auto transmissions no matter what engine (if 4wd)
Good overdrive transmissions (5spds) are really really hard to fit as well
I have a 78 cj5 factory drive train (6cly, t-18, D-20) and my drive shaft is like 13"
I was contemplating putting my 4BT in my CJ5 but I just completely rebuilt it 5 years ago, so I got an old scout (couldn’t find a good CJ6).
if I were to do it....
It would be best to a 4bt from a ford chassis, with a t-19, then adapting a Dana 18 with a warn overdrive would be easy,
mid 70s Wagoneer Dana 44 axles (both offset to passenger side),
just enough lift to fit the 4BT
The weakest link would be the Dana 18, but if you want good drivability and off-road capability you need overdrive. The warn overdrive only works with the Dana 18 but is one of the easiest ways to get an overdrive into a 5 (assuming you want 4wd).
But then again my 4bt, NV4500 and Bronco Dana 20 is just under 62” long so maybe it could fit, but I doubt it.
Big problem is the depth of the motor but if someone has put one in a 7 then it will fit in a 5 just need some amount of lift.