Ok, so I've been spending what spare 'truck time' I have in staging the engine to gearbox and mounting in the engine bay.
I need to cut off the old 3B Engine brackets and weld replacements in that align with the 1HDT position.
These new engine brackets are like hens teeth. In fact you can only get one side as the other has now been discontinued. I guess that's what happen when a vehicle is pushing 40 years.
Thanks to Dave, he's found the following. Basically the engine brackets from an HZJ73.
51421-60140 5,790yen
51422-60140 Delisted
So my plan is to obtain 51421-60140, bolt it to the engine. Have the gearbox bolted to the engine. Then lower the whole lot into the engine bay, bolt the gearbox into it's mounts and then position the engine so that the one engine bracket is in the right position. That will at least give me the correct spacing and I'll just fabricate the other side.