Very cool to see more of these popping up. I'm kinda planning on doing my own but I'm on the fence on whether or not to keep the gas engine. It's being a PITA right now but when it ran right it was just so cool.
I'm not real wild about that motor mount mostly because you can't use a finned motor, I'd prefer a normal style mount that bolts up to the front and something in the rear to support the long motor (don't want all that stress on the front endbell or mounting screws). IMO a 1521 would work, 1527 would be much better, and a 2215 would give you the power to do whatever you want. Go 2230 if you want to blow up gears and snap driveshafts like twigs

I like the 1527s as they are easier to get and $200 cheaper than a 2215 but the size and power of the 22 motor is very hard to turn down.