Has anyone thought of this...Just mount the engine/Tranny without connecting the shafts and shifter assembly to test run the engine and if so what was the proceedure?

You doing this in the car or on a stand? I started mine on a stand so I could check for leaks and I left the clutch disk out so there wouldn't be any chance that I would have the output shafts turning. (Safety, kids around). If in the car start it in neutral so you don't have to drop it again and add the clutch.

Dave

I will have the tail end up to install the engine/tranny and thought I could leave the shafts and shift shaft off until I check everything [after 20 mins or so at 2000 rpm]. This way I save a few steps if I need to pull it back out.

Any thoughts/suggestions?

Dont see a problem starting it in any gear with the axles out. 2 smooth round disks turning whatever direction one would have to try to hurt themselves on that. It cant hurt the gearbox. Note about oil leak SirAndy of this board found a nice one on mine. If you remove the Tstat pully from the block put short screw and washer back as that hole goes deep into the block and oil.