Bike carbs and bike throttle bodies are two different things.

If you check out this months Fast Ford there is a 3dr with a 2.1 pinto running 38mm gsxr carbs. The manifold is home made and the carbs are spaced to suit.

You must bear in mind that these carbs are CV and therefore the bore is straight through. A 45 side draught will in fact run a 34 or 36mm choke.

I had helped setup the 3dr and have to say that the bike carbs are very easy to tune compaired to 45s. More like hi tech SUs.

I used a seperate dizzyless, coilpack mappable ignition on the 3dr.