I have seen a lot about upgrades, but most involve a 16" wheel. Are there really any options for upgrades, front or rear, for 15" wheels?

I read some say the C4 non-HD upgrade may fit the front.

 

I know the 1LE PBR brakes on the rear JUST fit in the stock 15" wheel. Don't know about the front.

 

Aren't there differences on the inside diameter between the different styles of 15" wheels too?

 

Yes, and that is what makes it hard to say that a certain kit will universally fit any 15" wheel. There is a large variation of inside clearance on OEM 16" 3rd gen wheels, so aftermarket will be worse.

 

I have OEM wheels, but I figured there is some variation. Looks like I will have to upgrade my wheels if I want to upgrade my brakes.

 

I'm running a disc rear from a 94 firebird on my camaro with the stock 15" wheels. It has the LT1 rear disc brakes on it and I've had no clearance issues at all. From what I've read on here, the C4 non-HD front brake upgrade will fit. I hope that is true cause I've got almost everything needed for it, guess I'll find out for sure once I get around to installing it.

 

Are you running a 4th gen axle, or a 3rd gen axle with 4th gen rear disc brakes? Was there a difference in rear disc sizes in 94? If it is a 3rd gen axle, is there a thread about the swap or care to share some details?

 

I'm running the while 4th gen axle. I didn't want to deal with swapping the brakes over to my thirdgen axle. The whole thing is pretty much bolt in and go. It is about and inch or so wider at each end than the stock thirdgen axle, so my tires stick out a bit further than before. No changes in handling that I have noticed though. Mine also seems to be offset a bit from one side to the other(maybe 3/4"), but I recently picked up an adjustable PHB to fix that.

I haven't measured, but I'm pretty sure the discs are 11" in diameter.

You can certainly mount the 4th gen rear discs on a thirdgen axle. Member ebmiller makes the mounting plates and has a very thorough thread on here detailing the swap.