In addition to Sheldon Brown's info (too bad the master has passed), I found this last night...
mattsbikes - Step-by-step: How I made a home built tandem bicycle on the cheap.
AND, he is in the Salt Lake area. I will probably try this method first, out of expedience. But can add tube and reinforce as I go. Now all I have to do is be patient till I pick up the bikes tomorrow!!!
Of the various bike parts resources, none have tubesets and lugs for tandem specific applications.
I found Atomic Zombie's website... WOW! Over the top on everything...
AtomicZombie Recumbent, Trike, Chopper, Scooter and Electric Bike Plans
I've looked at great length though this site and others, and think I have a good idea how to setup a rear for a trike.