Update, a month of weekends away finally, with the kind help of my father-in-law, the new hot water heater is in and running.  Only about 2 hours or so, not bad!  The cold water lined up pretty well, so we plumbed it.  The gas worked out with some rearrangement of parts.  The hot we used the flexihose, but maybe we’ll re-plumb it later if water volume is a problem.  Leveled with little bits of copper pipe, like the old one.
Hot Water Heater
Cold
Hot
Gas
flexible hose!
the monolith
Goodbye Rusty!
Space Prepared
Cold Water
Gas
Hot Water and Vent
Light It Up
Hot, Clear Water!