[Christ]

For steel, you could always sandwich a couple pieces of body metal together, and glue laminate them, drill/mill as necessary. It would hold up just fine.

It would end up exactly like a MLS head gasket, only with sheet metal that would normally be used for body work.

For mocking up purposes, if you have nothing else to work with, a couple straps of steel bent and bolted to the face of the motor, then bolted to any of the mouting points on the transaxle would allow you to straighten things out and mock them up until the plate gets there, and plywood or 1/2" MDF would probably work as well.

Whatever you use as a temp plate until your stuff gets there, make sure you account for thickness of material, or else you'll end up with a "how not to measure twice, cut once" thread.