for what its worth i was gonna twin carb a K series engine with motorbike carbs off a GSXF or something (forget which now) as they're 36/38 or 40mm...... anyway, i found a company who were gonna make me a manifold specially for them carbs to fit a K series for just under 200 quid, and something like 260ish quid if i sent them the carbs as they would strip/rebuild/rejet and send back ready to bolt on and use. so they say. but i didnt do it so dont know what theyre like but sounded nice on the phone. i might be able to dig out a telephone number if you want it?