I do not know if this will be helpful, but when my husband did our frame off on our 1963
Bambi he replaced all the water pipes with pex... drew a plan first, and then just started with the hot water heater (if I remember correctly...) and went to the next water need. He worked the plan from the original pipes (which were all cracked, broken due to freezing by PO). I do remember making several trips to the hardware store to buy pex parts... began with the fancy crimper tools and such.
Here is a link to his thread on the restoration when he was working on the pex:
Good luck! Oh, and after he re-did the pex he pressure tested it first with air before enclosing anything...
Mrs. NorCal Bambi (traveling in S Tardis)