/6 to 360 engine swap.Can I use '81 Ramcharger parts

As noted, the oil pan and exh manifolds will not work in the Dart. Also, even if the ramcharger is 2WD, the tailhousing will not fit the A body trans tunnel. (the retainer clip on the rear bearing is on the side, not the bottom, so a regular pass car tail is needed. I would find a 904 transmission. The 9 1/4 is a waste of effort, try to find a later 8 1/4, or 8 3/4 for it.