I Have 3" True Duals With Glass Packs And Full Length Summit Headers On My 85 IROC. The Shop That Fabricated Them Said That 3" Would Definately Cause A Clearance Problem With The Rearend Not To Mention The Excessive Heat To The Fuel Lines And Etc. So They Dumped Just In Front Of The Rear Tires. They Had To Cut The Flanges From The Headers To Make The Bends Around The Frame. Was Kinda Pissed At First, They did It Without My Knowledge, But The Sound Is Great And Don't Have Any Clearance Issues. Definately Not Street Legal Tho. Cost Me $500.00 To Get It Done. Sick