I'm looking for some 15x7's to fit my P5 for my track tires, just have steelies now. What should I look for offset? 42?
Yeah, they won't. I tried it already. You'd need about a 38mm offset depending on your shocks, you'll need to trim out the fenders, and you can at best do a 225 in the back and a 235 in the front and it all has to be "perfect" and run relatively agressive negative camber to get them to tuck in. So no go.
You'd need an extra 1/2"+/- of fender on a P5 for this offset!