Flatman, what I did on my Old's motor is made it in three pieces: a flat "motorplate" that goes between the stock belhousing and the transmission (and used a longer pilot bushing in the end of the crank), and a two piece "clamshell" (top/bot) which bolts to the plate and also horizontally to the other half (with a opening for the clutch fork), and butts up to the back of the block and oil pan (the Early Old's have a cast in place belhousing that is part of the block).
This is all built out of 1/4" steel plate (legal on motors where no approved steel scatershield is available) and as for the clamshell halves, I made a pattern and took it to a Heavy Metal (Iron or Sheet Metal) shop and they "bumped it into the shape I wanted with the top and bottom flat and horizontal for about eight inches and then rounding 90 degrees at each end.
Bob