Just for the record: what I tried to describe above is from 30-some years ago when I swapped an LA318 from a '69 Dodge 3 speed pickup in place of the original Poly in my '67 Town Wagon.

Had to move the stock front motor mounts on LA block. I used the Poly bellhousing on LA318 block because that's where the rear motor mounts were. I think 1 bolt was different on bells. I kept my NP 435 4 spd. 1" 10 spline in the '67. Can't recall what I did on the flywheel & clutch, but I used the Poly starter on the LA block too.

I then stuck the Poly engine into the '69 3 speed truck. Swapping both engines was pretty easy and I used all stock parts. I know it works becaue I did it.