Yo really only have 2 choice's , 1 is you have all the parts for a real nice built truck, but that road is not for the weak at heart ,or wallet
but you are real close to what you have wanted all along so my vote is to build up a mild short block , pretty much stock except for cut the pistons , through some rods , head studs, and key ways in it and it should be a fun truck .
2. would be put a stock motor back in it, sell of the goodies and get out of the game .
Good luck it isn't an easy choice , every one will tell you what to do , but its a little diff when you are the one fitting the bill .