You can use the Tekno mount and not use the clutch, but the mount makes the motor sit a little further back and requires the pinion to sit a lot further out on the shaft. This places more lateral stress on the shaft and bearings. Don't know if that's the conclusion you came up with...
You can shim the front of the mount to sit closer to the spur. That way you can use std pinions. Or buy the long shank pinions that impakt sells (or mega). I would prefer to make some spacers due to what Brian said...