I`d be using a 56a Manual bellhousing section, not the auto bellhousing for a cut and shut job. The block is for holding the bellhousing square and to stop shrinkage. The block is heated as it has the greatest mass, the heat transfers into the belhousing for pre heating purposes. If you try to weld something like this without full preheating it can/does crack along the weld as you are welding. The welded bellhousing has to be left on the block until fully cooled other wise it will shrink and will not go back on the block. Once cooled it has to be remachined.

A late model T5 6Cyl box would be a reasonable start for a conversion. I`d still need to know the input shaft total length from the bellhousing flange to know if it would work.
D, If you find one on one your PAP tours let me know i`ll pay you to pull it out.

I might be able to make a machine that can grind the input shafts while in position. Im not sure how much it would cost to get them done elsewhere. Otherwise we could set the gearbox back a bit and put a spigot bush in the flywheel and not modify the input shaft.

Those corolla folk are bloody lucky!!