It's ALIVE!!! Started first thing this morning.

Had to mount it back on the frame to use the throttle lever. It was a lot easier to start having the added stability of those large rollers and the leverage you get with the engine being down low.
Damm vibrates a lot at full throttle, can see why those frame rails cracked.
Link to a short 4sec video of the engine on the lawnmower.
Briggs is finally working!