where do you guys stand on this idea?

The aussie 245 and 265 will fit under the bonnet (hood :P) of an A body, so the 4.0 Jeep should.( The black '70 Valiant in my avatar has a 265, and the same hood height as a 69 Dart)
I can see lots of good points for it, most have been mentioned.
A turbo, EFI, 5 speed, 4.0 in a '67 -'69 Barracuda would be quick, fast, and make jaws drop.
And, if you were good with your hands, not too expensive.