Do you know what is on the car now? Does it have a cage? Does it have a logbook?
I don't know a 15x7 w/ +50mm offset, I do know that Volk makes them in +48mm though, they are a little pricey though ($350+ each) and they generally have a long wait time. You would be best off trying to find something used. The Prelude has the same lug pattern as the Acura Integra Type R (ITR).
There are three guys here (or used to be here) that run/ran track Preludes... 71dsp, DR, and Honda318dx. The last guy sold his car, the first to guys don't visit here anymore... they post on North Texas Prelude Owners Group Forum though... (
http://forums.n t p o g.org/ ... take the spaces out).