[MJN]

Thats really up to you and what your end goal is and what kind of rig you're building. Do you want a 4x4 daily driver or just a show piece? Full on factory restoration or resto-mod? In order to find out what axles and drivetrain is in it better pictures would help. I'm only guessing based on the front axle picture that the drivetrain is from a '78 and newer pickup/blazer or suburban. Having pictures of the transmission/transfer case, rear axle, etc would help narrow it down.
If you're going for a total original restoration, find an original drivetrain from a '57. If you want original four-wheel drive, you'll pay for a NAPCO conversion if you can find one.

I'd start with getting yourself a factory service manual, owners manual and a few other reference books to help decode things along the way, reproductions are available from LMC truck or several other parts suppliers. A copy of Cars and Parts Catalog of Chevy Truck ID Numbers 1946-1972 is helpful https://www.barnesandnoble.com/w/cat...=9781880524022 . Download a copy of the GM Information packet too, https://www.gmheritagecenter.com/gm-...tion-kits.html