The mounts are the same on the B13 and B14 5spd SR20's, but they are different for the P10 and P11 G20, B15 Sentra SE, and non-SR20 B13, B14 and B15. (Also the tranny mount is different on an automatic SR20.)
So in other words, the ES mounts that are made for the '91-'99 B13/B14 SR20's will not work on the P10 and P11 G20 (I've heard only one of the mounts will work, but not all four.) Be patient, though... I know someone trying to prototype a set of ES motor mount inserts for the G20.