I thought about dropping a 12V in an Imperial for a driver. It definitely has the length.
After measuring the CTD in my 92 D250 I can see that I'd need to take 4" out of the oil pan and modify the oil pickup. Stuffing an OD transmission and 2.94 gears out back would have it singing a happy tune.
Larger T-bars can be made and the front end already uses light truck components.

A 4BT is a great swap for a lighter car but it needs to be leaned on a bit to run well in a big car.