I recently got myself a 1990 irocz and I'm not happy with the brakes, I was originally thinking of upgrading the stock system(new calipers,rotors,pads,and lines) but then reading through the forums I've found upgrading to a ls1 setup is rather popular. Is it really that much better to get the bigger rotor size, I would change the calipers over to a aluminum single piston design anyways, so AFAIK it would just be the larger rotors that would be different than if I upgraded the stock system. Also if I were to change to an LS1 setup I'd buy new rotors,calipers,pads and lines, what else would I need to convert to the LS1 setup. I have 16inch IROC rims btw so the LS1 setup should fit from what i've read

 

Bigger rotor means more stopping power so yes look into the ls-1 brakes im actually doing my ls-1 brakes really soon gotta drop the spindles off at machine shop for him to drill and tap the mounting bracket holes for the ls-1 calipers then ill get the longer studs calipers, rotors and pad and see how it goes from there i dont know which master cylinder u have to use though

 

Just go to bigbrakeupgrade.com. Scott can hook you up. If you really enjoy the fab work he will sell just the adaptors. But I recommend getting the whole assembly ready to go if your skills are limited. I just finished the conversion on my 89 (with stock rear discs) and it is great. I don't know yet if it stops shorter but the pedal effort is much less to stop the car. I have worked this car from end to end and this is one of the best investments I have made so far. Go ahead and upgrade to stainless lines. You should expect to spend $800 or so.

 

This website will give you an idea of what's involved. I've done the job on my own with only the machining of the 3rd gen rotors into the hubs required that needed to be farmed out.
http://lukeskaff.com/?page_id=329

I also purchased the abutement brackets (caliper mounts) from Ed at FlynBye.
http://www.flynbye.com/catalog/i36.html

He also sells the full kit (as do others as was posted above)
http://www.flynbye.com/catalog/i47.html