We have pieces of flat plate on the inside floor that the bolts go through, that are welded into position and curved partway up the tunnel for extra strength. The gearbox crossmember is just a big piece of 8mm flat plate that bolts to the toyota gearbox mount. We just sat the gearbox in position with the jack and bent a piece of wire for a template and the bent the flat plate to match.
We measured the length of the bellhousing of a dellow kit and used that as our target length, I might be able to crawl underneath and give you a rough measurement a bit later.
The front casing of the 56a was cut through just behind the plate where the front bearings locate. The back plate of the toyota bellhousing where the seal housing/realease guide bolts to was cut off as well.
Then both parts were milled down on the sides that were cut until the correct overall length was reached. A sleeve was made in a lathe in order to centralize the two parts and then we got stuck in with the mig welder.
After that we chucked the whole lot in the lathe and turned out the input shaft hole in the 56a bellhousing so we could bolt the original toyota relase bearing guide onto the toyota section of the bellhousing.
The toyota release bearing guide was turned down and the datsun bearing carrier was bored out so they worked together. The rest of the clutch setup remains original datsun stuff.
The input shaft doesn't stick out past the bellhousing like in the datsun box, this means the spigot bush or bearing has to go into the flywheel.
Other than that its a nice simple job.
I'll get measurements later.