Lisa took the oil cap we bought yesterday and drilled a hole in it big enough to hold the bottom end of the filler neck.
With a bit of work, she was able to get the improvised gasket into place and get the oil neck back where it belongs, including securing the other end of the filler neck to one of the bolts that holds the alternator in place. I have no memory of having removed it this way, and it doesn't show up properly in the photo I took of the burned up alternator before I removed it, but everything fits.
With both the air and oil parts fixed, Lisa got the "doghouse" secured. Unfortunately, in my exhausted zeal to force the engine cover back on after the Alternator Madness, I partially broke one of the latches that holds the cover down. It's not a serious problem, but it's something we should get fixed. But getting a replacement latch is tricky. However, there's a Pick-and-Pull in Sparks whose inventory claims to have two recently-acquired 1986 Astros, and the parts between the 1986 and 1987 should be virtually identical, so sometime relatively soon we'll try go to Sparks and see if we can salvage the necessary parts to replace the latches.