I have a H22A but I have been told that a B18C5 throttle body will bolt right up. I have also heard that a F20C1(S2000) TB will bolt right up to a B18C5 (and therefore a H22A). Is this true and what are the diameters of the B18C5 and F20C1 TBs?

 

I dont know about the F20C TB but the ITR is 66 outer side and 62 inner.
Stock H22 is 58 inner and 62 outer