Gene covered all the major points very well, as usual!
I will add that since you mentioned a tight budget that the 2 best things to do is either buy a properly done project or done car, or buy a donor vehicle for the drivetrain swap.
Getting a 92-95 Dakota will net engine, trans, driveshaft, wiring, a trans crossmember and engine frame mounts to modify, along with gagues, seats, and a bunch of nuts and bolts. This stuff really adds up if bought separately. The rear axle won't be the right width and has the funky 6 bolt pattern, but a 67-70 B body 8.75 is probably a good fit.