Picked up the car, with the e36 M3 muffler installed, from Bimmerworks (West Chester, PA), who did kick ass work (as always).
The result was EXACTLY what I was hoping it would be-- as quiet as the stock e46 m3 muffler and zero drone, under any conditions. It actually seems to have a bit less rasp, too! (better, imo). Will post a video at a later date. Not sure if it'll be before or after I do euro headers/catted section 1/tune.
My request to them were...
-stock tip location
-stock section 2 merge point retained
-bolts up to stock section 1 like stock
-if possible, retain the stock section 2 resonator
-use OE hangers for future serviceability
Pictures of the process...
Test fitting
Stock e46 m3 cut off after the resonator. Fun how the e46 M3 doesn't use round pipe while the e36 m3 muffler does :P. They had to reshape the e36 pipe to match.
e36 m3 muffler with the necked down portion cut off. The e36 euro (s50B32) and US (S52B32) muffler are both the same, other than the necked down portion where it joins with the mid pipes. My thought going in this project is that if it flows well enough for the 321hp 7600rpm S50B32, it should be okay with a 343hp, 8000rpm S54B32. Butt dyno says that assumption was accurate.
e36 M3 muffler welded up to the e46 M3 section 2, with e46 non M hanger mount points added. The muffler body was painted black to minimize the saggy muff/full udder look that e36 M3's sometimes have from behind/side.
And installed!
The muffler body is above the line between the tip of the exhaust pipes and the tires, so my departure angle shouldn't have been adversely affected.