Jeep 4.0 in 69 Barracuda

...horseshit...a sherman tank V8 has been shoehorned into a '70 Mustang before...a 5.9 Cummins will fit...it might not be pretty, and you'd have to do some serious engineering, but it can fit. That being said, if you wanted to drop a diesel in a Dart, use a 4BT...smaller, only weighs as much as a big block, and you wouldn't have to do quite as much to get it in there.