Leave the motor mounts off, I would adjust the angle of the long block with a tight (sturdy) chain on the "cherry picker" hoist. I also leave the vacuum pump/ps pump assy off as well to facilitate better access to the ds motor mount bolts.
You can gain a bit of room by removal of the valve covers at the rear and masking the top of the engine to prevent anything falling into the engine or push rod tubes (Mr Atkins is cringing by now).
You can also remove the oil pan and pick up tube, then reinstall before lowering and installing motor mounts (once its in the chassis).
You can also loosen the cab mounts and lift the cab up a tick and slide some blocking in between the cab and frame mounts. Even a inch or two at the firewall would work miricles.
Assure that the steering shaft, wiring, brake lines, a/c hoses (if still attached) have enough slack to allow this or remove as necessary to prevent another "money" pit.
Some smart welder types like Evan Beck's trick. Zip out the cross member with a plasma cutter and then weld it back when you are done. This would be my last resort, as I only know a couple of people I would trust to weld it back properly to assure structural integrity, et al.
Good luck,
Andy