I'm interested in this because I want to do a cab/frame swap too but questions about yours.....
How did you get from this point:
to this point:
?
Obviously the cab isn't high enough for the frame to be rolled backwards for the engine to clear under the cab.
And the rear cab mounts, seen in the pic, are too tall (cab not high enough) for the frame to be rolled forward under the cab.
And the wheel track is too wide for the wheels (bare rear end or the bare front hubs) to fit between the wooden supports you built for the cab even if the cab was high enough to clear the cab mounts or engine.
Did you end up having to remove the rear end from the frame & then roll the frame forward on the front tires & a floor jack under the rear of the frame?