02BEAST

iTrader: (8)

I have prostars 15x3.5 using a 5/16 spacer ,15x10 with no spacer will 2.5" studs work?

Photochop

iTrader: (74)

Yes. Stock stud length would even work on the rear with no spacer, just make sure you run the longer shanked lugs - like the 1.3"ish models mcgard makes.

02BEAST

iTrader: (8)

Will the 2.5" be strong enough also? I'm putting a 5/16 spacer up front I can still use the 2.5" studs there.

Mean Green z28

iTrader: (17)

As long as the shank of the stud is long enough to go all the way through the mounting hole and have at least 1.5-2 diameters of thread engagement, you should be good. I had an issue where the lug nuts I bought weren't long enough to go the thickness of the wheels and had them come loose on me on the highway ... not fun.