need a little help with my calipers

[cjlz31]

Hey all i have an 88 z31 that im fitting an s13/14 suspention on and one issue im having at the moment is the size of my calipers. I recive a set from an r34 gtt (im guessing) and i belive the front require i use a 310mmx30mm rotor. What is the minimum size wheel i can use (i have a set of old 16" riken mesh wheels) and is there an other option rotor i can use other then getting a set from Aus or japan. I live in california so it turns out that some parts are harder to get a hold of then others. Thanx in advance!!!!