welcome to the shop JC - have to know a lot more about the truck condition and your plans to judge estimates, and you'd have to know what trans and rear were suggested as well as what you want to do with the truck - does it need a totally new drive line? .... sounds like he wants to build you a hot rod with bits he can get readily, you might prefer to keep it more original and 4,500 would go a long way on body work and paint
Bill