It was warm yesterday (38F), so I got a bit more done.
I had 1/4" MDF left over from another project, and it turned out to be perfect for mock-up of the brackets. The side trans/engine bracket will be 3/16"x1.25" steel bar and 1/2" ID steel tubes (engine bolts).
The rear bracket will be a .375" thick 3"x9" aluminum plate. You have to remove some block material behind the halfshaft's upper bolt, 1/8" at most, for the bolt head. 1.5"x7/16" bolts will be best for the HS (3/8" shown), and 35mm long M10x1.25 bolts for the 3 block holes.
Another angle showing both brackets:
The front bracket, something I've never seen on any other no-kit H2b, will be 1.5"x1/8" angle iron. I'd love 1.25x1/4" for strength, but *anything* here is above and beyond what has worked for other people. IIRC the F22 has an untapped hole at 119mm from the trans and an undrilled hole at 75mm. The H23A has 2 tapped holes, one at 74mm out and the other at 103mm. I'm holding up the angle iron in place of MDF in the pic.
All that's left is to cut, drill, and weld some steel & aluminum. The rear t-bracket is very minor, I only have to cut the ears off and weld some plate steel on. I'm hoping if I drill holes for a B and H2B swap, it can be used for either engines.