I was under the impression that:

USDM:
RSX-S - K20A2
RSX (base)/Civic Si (EP3) - K20A3

JDM:
Integra-R - K20A


but then I was reading something and came across 'K20C'...I'm a little confused here. What car does this engine belong to?



Here is something else I found about it:
'n/a K20C1 JDM All 3-door Type-R' (civic)