The 318 in the pictures is a newer motor then what came in that truck, there may have been other upgrades done when the motor was installed. Originally it probably would have had the poly 318 with a 4 speed, or a flathead 6 that may have had a 3 speed. Very few V8 trucks would have came with a 3 speed.

That one looks pretty solid, but understand very few replacement parts are available for that era Dodge truck, what is there will likely be what you live with for original parts.

I had a 58 once, I was going to build it, but my brother in law talked me out of it. He put a 318 ,727 in it, got it painted, and sold it to someone else. I didn't know he was selling it until a month or more after it was gone. Gene