Single straight pipe right to the rear bumper on the 52 Merc works for me. Not real loud unless my foot gets to heavy on the gas pedal. At idle you can hardly tell its running.You could always take the muffler out and run a straight pipe all the way back, ain’t nothin like flathead music!
https://www.youtube.com/results?search_query=flatheads+with+porter+mufflersThink I’ll check out the porters,then find a good buddy that has a lift,,
A good project for someone would be to make recordings of the different muffler sounds and put it on u tube!,