Converting from a three speed manual to a 4 or 5 speed

I have a 1972 Duster with a 318 and a three speed manual with a hurst floor shift. I am just starting this restoration. The engine is the original with matching numbers so I will hot rod it but keep the 318. I'm having trouble finding info on manual transmissions. Is there a 5 or 6 speed manual I can take out of something modern that will fit in my duster. The only options I have found is either an early Mopar 4 speed which I think will bolt right in or a very expensive Tremec 5 speed. I won't pay $4500 for the Tremec but I could live with a 4 speed. It just seems there should be a junk yard option since Mopar is still making a version of the 318. I think a modern Dodge Dakota has a 318 w/5 speed option. Will the Dakota tranny work? Any advice would be appreciated.