Go for the Gen III. The change over has its challenges, but what swap doesn't ? I think it looks like it belongs! 1970 Duster. /6 k frame, torsion bars, manual steering with unmodified steering column and column shift.
I used 5.7 Eagle exhaust manifolds from a Grand Cherokee. Opened them up inside and they already have a 3" collector. Very happy with the fitment. As for manifold performance? Don't know, but I'm sure it's better than it was stock.
I don't have any pictures of the Grand Cherokee exhaust manifolds. They were only modified internally. Right side manifold was not touched on the outside and the left just needed a small relief for the steering coupler.
My engine is a 2005 short block from an 05 Chrysler 300. Heads are port matched and blended Eagles using stock length Eagle push rods, stock head gasket and modified Grand Cherokee exhaust manifolds. 60 psi oil pressure cold and 35 psi at temperature. This thing has a bit of compression and...
I used both ports in the non vvt cover for the temp guage and coolant sensor. Idler bracket was made and the pulley is part of the truck A/C delete bracket and pulley. I'm also using an under driven crank pulley. Catch can and oil cap made by me as well.
Maybe this helps?
Modified the K frame to use the car timing cover. Alternator is tight. Best fix for that is to machine the alternator mounting surface about .060"- .080".