If you have a '52 serial 25372 or prior, the right and left muffler assemblies which includes all the clamps, exhaust inlets, heat shroud and hardware, are exact duplicates. There is a different left and right exhaust stack however.
If you have a '53 serial 25373 or later, the entire muffler system is the same as that for serial 25372 and prior except for the right hand muffler and head shroud parts.
An entire muffler system from a 172 serials 28000 to 47746, if it uses the original part numbered parts, is the same system as that in a '53, serial 25373 and later 170B. Muffler systems found on 172s after serial 47746 are not the same as the earlier system in that the diameter of the muffler cans are bigger and as reported by Canav8 quoted below, the exhaust stack diameter is bigger and perhaps some other differences which might interfere with direct installation on any model of 170.
Moderator Note- Most of this info was originally gathered and posted in a TradeMart post. As TradeMart posts are deleted in 6 months the info would be lost, thus I've posted it here as well as directed that any further comment about muffler systems be directed to this thread.canav8 wrote:The 172 Hanlon Wilson cans are larger exit port. They are 2.25 diameter instead of 2 inch. Different part numbers. No they are not higher performance either. D