It took a while to resolve but finally everything is 99% done. The coolant problem was most likely caused by a bad (and brand new) thermostat. After adding aircraft piping with stainless heat jacket (see picture) we had some success but a small leak caused by npt and straight thread being incomparable. Eventually I changed to -16an and things are working fine.
The radiator was replaced and -16 fittings welded on. There was a need for a shaped flexible coupler and so the piece below solved the problem.
At this point things are lined up and ready to head to the tuner. Hopefully we get there one day soon. The car has 25 “neighborhood” miles on it and feels good. Still only 4 forward gears but fine for now.