I've got my 4.0 TJ for that though, 20K miles from new
I did always want to turn it into a pick up with the AEV Brute kit though. The Jeep 4.0 isn't that much more sophisticated than the Flattie, and just as heavy
At least I can get alloy heads for the Flattie.
Swapping to a later model frame is a bit complicated here as you need to bring the old body up to the standards of the year for the donor frame.
I'm meeting up with some rodders I know at the weekend so I'll hopefully get some pointers.