I'm not a fan of frame swaps though there are advantages, modern suspension with r&p steering, cruise control and some others. The disadvantages using a Dakota frame are body mounts, gas tank location, 6 lug wheels, the truck has a higher stance and the wheelbase has to be spot on for the wheels to be centered properly.
If it were mine I'd probably update the original frame and drive line. The 318/340/360 would be an option though rebuilding one will be more expensive than a small block chevy, but a 318 build with 340 heads, mild cam, headers, and 600/650 4 barrel of your choice will make decent power for the street. If you go fuel injection I would stay away from 91 to 93 Dakotas as they were OBD-1. Keeping the build all Mopar, IMHO, is a plus though more expensive.