look for parts out of a 92 d150. the later gen 1 rams came with rollers, basically an LA bottom end with near-magnum top end. if you go rollers, you'll need the new roller cam, oil through push rods and new roller lifters. the push rods are where you might hit a road block on availability or spend some cash unless you go pull them from the junk yard for cheap.
If it's a project however, you can do a complete Magnum top end swap with zero issues. you need roller cams, lifters, rockers, the oil through push rods and magnum heads. I believe the intake manifold is not compatible. Magnum heads breath better anyway. there's also a bit of fussing with the front belt drive brackets. so if you can, go to the junkyard and grab the parts as well as the front belt drive brackets. or if you want to get really fancy, find an early gen 2 ram or grand cherokee and get the serpentine bracket. this will require a reverse rotation water pump however, tensioner and steering pump/alternator pulleys.
EDIT: I just looked on Rockauto, push rods are available and cheap. so are lifters.