the k20a is found in:
2001-2005 Honda Civic Type-R (EP3
2001-2006 Honda Integra Type-R (DC5)
2003-2006 Honda Accord Euro-R

and the k20a2:
2002-2004 Acura RSX Type-S and 2002-2005 Honda Civic Type R (EP, European)

according to wiki anyway.
I have seen a few really sick s2000 (F20C) engine conversions, in such cars as the hatchi-roku (ae86). by all means they are amazing engines capable of producing awsome power but some people believe it to be blasfamy to do the conversion. if its power you're after and you have the money and time i say go for it.

Im unsure if there is a b16a rwd gearbox like tyrie said. Not a honda expert or enthusiast after all

Ask around on the honda forums and such if there is any rwd boxes, i dout it.