109 throttle quad- nice project
as it's basically a rectangular box with very near 6" diam circular bit on the back, I'd be looking for something like a 2" slice of 6" diam plastic drainpipe, (chop out a ~100 deg segment for pushrods if using linear pots?), cut slot(s) for levers and sandwich between 2 ply plates for the sides. finish of rest of front box with ply.
Thickness of slice dependant on what thickness of wood you use for the plates- total width of unit should be ~55mm.