two piece to one piece drive line swap.

[Clavo106]

My truck c10 has a th400 with and 1968 1/2 ton diff. Has a two piece drive line. Im all ready cut the frame and and welding everthing up (lond bed to short bed) just doing mock up stuff now.. I was planning on running the two piece. But if I could go one piece and pick one up from a wreck yard and have a shop cut it down.to fit.... what would I need to get this done...fit and vehicle wise to look for?.. done easy I guess.. lol..