The factory v6 exhaust is 2 1/4"s. The factory v8 is 2 1/2"s. But the v8s exhaust is wider because of the size of the engine. The long tube v6 headers are 2 1/2"s but adding a v8 exhaust is too wide and will not match up. The v6 exhaust pipes are 1/4" too small and the v8s are the right pipe size, but will not line up properly. I recommend going to a exhaust shop because they do not use pipe clamps on the exhaust (that break eventually). If your car is lowered do not use long tubes.
Using long tubes would also eliminate your egr system. It sends exhaust gases back into your lower intake. I recommend a tune so your car does not run lean and cut off some times.
new engine,1.7 rocker arms,Pipes exhaust, shorty cats , shorty headers,under drive and overdrive pulleys,4.2 upper plenum, throttle body spacer, cold air intake, stage one clutch, shorty shifter, and tune. 8.8 in storage