need brake help tonight!

[cdlong]

i want to upgrade to 300zx brakes but i can't afford it nor do i need it right now. but i do need new rear brake pads. i was just going to replace the rears with cheap pads from autozone until i can afford nice pads, calipers, rotors all aound and a master cylinder.

well, as luck would have it, as i was finishing up putting in the second set of pads, the caliper sprung a leak. i wasn't planning on upgrading to 300zx rears but i did want to upgrade the rears somehow. i heard that the jdm S14 rear calipers had a bigger piston (as well as 300zx fronts, but that's not important) so i was thinking of doing that.

time for the questions. should i just fix the caliper and go on my way, or should i upgrade the rears while i'm in there? if i should upgrade them, is there something i could do by tomorrow? like S14 w/ABS calipers or something? is the upgrade really worth the time, or should i just get new calipers since the parking brake arms are virtually frozen anyway? i don't want to spend my time rebuilding the caliper if i will just replace it in a month anyway.

does anybody know the piston size of the rear calipers? for S13, S14? fronts too if you can. also the piston size of 300zx fronts

thanks