Come on guys! You have a shaft that needs to be turned ,the blower, and one that is turning, the engine, any of us with any level of fab ability can make that happen. I would probably go with standard blower pulleys and toothed "rope" to drive it. Lay the blower on its side, I'm talking 4-71, 6-71 etc GMC style roots blower here, with the inlet on one side and the out let on the other and I think that the biggest fab challenge is making a good plenum between the blower and the engine. Important to get the air slowed down and going in the direction of the inlet ports so I would do some sort of turning vanes internal to the plenum and I would make it BIG with lots of volume to get max pressure, evenly distributed to all cylinders.
Rex