measuring was challenging, as I needed to allow for the bits of dowel going into the fittings, but we got there!
The T fitting at the far end will eventually be fitted with appropriately sized bits to emulate the gearbox output plate, so that I can line the jig up with the propshaft. I may yet fit a false prop coupling on the end to ensure its 100% in the right place.
When its fitted in place, I can measure the gap between the bottom of the dowel legs (which are where the engine mounts finish)... I may make up some fittings to get an accurate measurement on the drop, spread and angles.... probably more accurate that way.
I can see myself with bits of rope and string holding the jig in the right place to make the measurements!