Jay; I realize there are a few other ways to get around this. But some of us have older cars that have few and far between accessories, so our engine compartments are wide open to what might look like a band aid treatment. Hell i didn't need to cut my spark plug wires to custom length or use SS fittings, but I did. Must be all them years of being one of those picky Machinist, I guess.
Cut the general outside shape and roughed the hole on a waterjet then finished the rest on a knee mill. I realize the FE had two sizes on their thermostat, this is the two inch one. I've been retired so access to shop equipment is no more
I still got the drawing if you like but it would be a no brainer for you after seeing all the mind boggling things you've been up to. You've done some great work (not easy), but maybe you'd like to fill a nitch for the everyday FE guy thinking about EFI.
Just a thought