I just checked it up and also looked at my Premier which has its original exhaust except the muffler. The pipes are 2" and the muffler is the same for 6cyl and V8 which is 1.75". It does appear to be a bit more complicated in HQ though as there is 1.75" chrome tips listed for 253 and 308 (although this may be for twin 1.75" tailpipes on 253) and the 350 engine fits in amongst it all too.