Long story short....
Hogged out stock intake hole, went clear through the wall and into the exhaust heat cavity behind.
Made a steel sleeve to slip inside to make a solid wall again
Brazed the sleeve in place, drilled and tapped the 4 surrounding casting bumps, and had a machine shop mill the surfaces flat and to the exact same height
Made skinny barrel nuts for the studs, the two bigger ones were Porsche 911 exhaust nuts, drilled and tapped to different thread size and reduced OD. They have a convenient 6-point Allen head at the end. The 4 smaller barrel nuts were brake line flare nuts, drilled and tapped and hex reduced to 10mm for extra clearance.
Got a block of aluminum to make a carb adapter out of, for the Weber 38/38 clone
bolted the sucka on with the recessed nuts
sandblasted the manifolds
Painted them too[img]http://sm.uploads.im/t/jmO6p.jpg
and replaced all studs with new. Currently waiting to find time to hang them on the car. Left a piece of aluminum sticking out of the adapter for now, in case I need to use it to fabricate a throttle cable bracket or something. Haven't thought that far yet, I'll burn that bridge when I get to it I guess.
Factory carb hole on the intake grew surface area by 46%, roughly the same amount the carb bore grew going from stock single barrel to two 38mm. The carb is a true 2bbl, butterflies open simultaneously.
I suspect this engine will make much more exhaust heat than needed to heat the intake, so I will be using the block-off LPG gasket between the exhaust and intake, and rely on conducted heat only.
Next step would be headers so this is not permanent.