where do you guys stand on this idea?

Hood clearance might be a major hurdle, along with length. The 4.0 is in many ways a more modern engine than the /6. The 4.0 is a 1986 redesign of a 1964 engine, while the /6 is a 1959 design. The 4.0 has a 7-main crank and a much shorter stroke resulting in a more durable bottom end at high RPM. The stock 4.0 head is no flow monster, but responds to porting well.

The best year group for a swap would be a 2000-2001, stay away from 2005-2006 (the OPDA was junk). If it were me, I would use a Megasquirt instead of the factory CPU which is really not performance mod friendly.

Transmission wise, there were various 3 and 4 speed 904 derivatives which could be mixed and matched.