NEVER EVER NEVER NEVER UNDER NO CIRCUMSTANCES PUT A NEW MOTOR IN SOMETHING YOUR JUST GOING TO TURN AROUND AND SELL!!
Don't do it.
Don't get it painted, either.
Why?
Because no matter what you do to it, it's going to be 'wrong' to every prospective buyer.. and you will very rarely get your investment back out.
A SOLID, rot free 1950 1/2 ton pickup with no motor or trans is worth every bit of $1500.. again, provided it's solid, and not full of bondo.
Now put a new motor in it, and you might have a truck worth $3500.. but it will appeal to about HALF the prospective buyers.. because the other half could care less about the stock engine or trans, and plan on cramming a 350, an automatic tranny, and a new rear end in it anyway.
Now if you just happen to have an old 216 laying around that's in good shape that you only have a couple hundred dollars into.. and you can put it in yourself on a Sunday afternoon.. then by all means, go for it.
But NEW motor and pay to have it installed? Naww.