help/advice 1980 dodge pickup drivetrain

I have an opportunity to buy/trade for a 1980 Pickup with a slant six and four speed tranny. I haven't seen it yet so don't know if it's a top-loader or what. Does anybody know if this tranny and engine will work in a 64 Valiant? The old 170 slant and three speed are about shot, they just refuse to die.