2. Carefully cut out the lower front engine mounts, re-install the engine into the engine bay, then tack weld the lower front engine mounts into place (top photo). This will allow you to finish re-welding them back onto the frame after you remove the engine (bottom photo). You can also see in the top photo how notching out the end of the downtube in step # 1 allows just enough clearance for the counterbalancer.
See photos below.