IRS Rear Suspension Page When I bought this Crew Cab, it already had independent rear suspension. The installation of IRS into a swingaxle Bus is pretty straightforward. Bus-Boys and Wolfgang Int'l have been selling these kits for years. Whoever did the conversion thought that gussetted trailing arms were necessary, but rear disc brakes were not! This conversion was fair. The shock location and mounts are a horrible after thought, but the tracking looks to be right on. These are the new trailing arms! I had them powder-coated black. Shocks have not been decided on yet. The new trailing arms have a different shock mount that cannot be used with the existing upper mount. More to come. . .