I'm Cummins swapping a '74 Duster, thought I'd share the progress.
Just a little update for the project.
The engine is rebuilt, (mostly... 99% there) and painted. Gotta wait on the fuel system, for now, (injectors and high pressure pump) since it'll be a $5,000 or more set up.
I talked to the guys at USCT (they're a bit difficult to get a hold of, but fantastic to work with) and they modified their chassis stiffening kit and beefed up the necessary components to 3/16" thick as opposed to the standard 1/8" material. Surprisingly not as expensive as it thought it'd be. Basically just doubled the price.
I haven't cut into the car yet, nor installed the kit I ordered from them, but I have it at least.
Soon enough, I'll be able to test fit the engine and transmission and determine how far back everything needs to be, as well as see what modifications will need to be made to the torsion bar cross member. At this point, that's the thing that spooks me the most. But I'm sure it will be fine, since the G56 is large around but a relatively stumpy transmission, I might not even have to cut into the cross member, especially since I'll have to lob off the stock motor mounts on the K-member to lower the engine a bit.
I've got my electrical mostly worked out, I'll be using a Painless standalone engine harness in conjunction with their full chassis wiring kit for the car. I'll need to repin the engine harness to get it to work with the ECM I have, but that's nothing major.