Tire Size ?

Ok this is for my buddy, He has a 98 cavalier wanting to go autocrossing this year he has already picked his tire Kumho Ecsta Supra 712 the closest tire size to stock they make is 205/55/15 he wants to know will this work if so how bad will it offset the speedo. Or do you all know if they make a size closer to stock now?. The rim is 6inches wide. I guess thats it thanks for your help.

most 205's will roll between 5.5-7.5" wide, 6" being a money shot and 7" looking a little stretched. If he wants to upgrade to a nice 17x7 check out the 215/45/17's, i have them on my car and they are quite nice.