You can always use 2 pieces of 1/2" thick flat stock with threaded holes to mount to the engine plate, and holes to bolt your engine to the flat stock.
The H50 on one of my Sears bike came with the clutch outboard, and the engine hangs way out to the right, but thats how they sit with everything lining up. You'll just have to set the engine on the frame with the rear wheel mounted, get everything square, and it will be easier to see what you have to do.