Tonight, I drilled the injector holes and welded up the motor. The injector holes were surprisingly simple to drill at 0.06", 0.022" and 0.013". I did find that the middle sized drill bits were only good for about 6 holes in the stainless.
With the exception of the spark plug bung, I'm very happy with how it turned out. Welding is definately simpler than trying to design, fab, and assemble a bolted joint.