The donor bike has been a mixed blessing. So far its biggest gift has been tires, though I am undecided on which wheels to use. The ones I initially thought to use are more period correct, high-flange Normandy Sports (marked "Schwinn-Approved!") laced to Araya 27s, but then I would have to factor in some cost on those, whereas these Maillard/Weinmann 27s would be free. Hmmm. Then I pulled the tires and perhaps this is my answer -

- I had never before actually encountered duct tape as a rim strip. I remind myself, well, this IS the South, but this kinda feels like a paradox. Our rule here is, if it doesn't move and it's supposed to, use WD-40, and if it moves and it isn't supposed to, use duct tape. But this is duct tape used on something that is supposed to move. My brain hurts. Anyway, I think I may just gently trim up the tape so it doesn't crowd the tire bead (or hang out over the brake surface) and relube the hub and roll with it, because nothing says clunker like duct tape.
I had thought I would use the seat post from the donor, but before doing that I took one last trawl through the various boxes of parts and found these -

- a steel 26.4 mm seat post thrown in when I bought some parts of a mid-70s
PR-10L and a Cane Creek seatpost shim I KNEW I had somewhere. And here it is. And while it IS meant to convert a 25.4 mm to a 26.0 mm, the shim itself measures at .37 mm, which means it adds .74 mm thickness when wrapped around the 26.4 post, which when properly greased will work nicely in my freshly honed 27.2 seat tube. So that's settled, especially since I have a saddle clamp and a saddle to complete the process.