Chuck,
I don't think you will find a twin gasser that will fit without the plugs protruding thru the cowl. You may get lucky. My 3W-157 in my 33% barely fits. The plug caps are actually in the blisters of the cowl with approx 1/8" clearance. If a plug wire tries to come off it won't go far

Thought I would show you guys a test rib I made in my rib jig for the Hatz. The jig works great now all I need is a bunch of wood to start building ribs.
Later!!
Anthony