The head gasket sealer seems to be working. I got it mostly street legal (Oklahoma is easy) on Friday afternoon. The cooling system pressure seems a bit high, but it's not purging coolant. I put some fresh gas in since it was about empty of the 2019 gas that was left in it.
I'll drive it minimally over the next two weeks, but enough to sort it out and have it ready. Hopefully it holds together and waits to die a proper death at the event.
My local Gambler 500 group has a very different perspective on the HooptieX than the RallyCross guys. I'm still deciding which way I want to go with this car.