The GMC CCKW

Could someone give me the dimensions of the cast muffler for the 105 leroi air compressor? I'd like to make one similar to the original. I've seen them in pictures and have been next to the one on Kevin Kronlunds truck, but never thought to get an idea of how it works or a rough idea of size. All I remember is it looks sorta like a mushroom. I currently have a cut down tractor muffler adapted to it, but after 6 years of running, its rusted out and needs to be replaced.

Mighty loud with just a flapper on it...

Huh? Whats that? I can't hear you, my compressor's too loud!
Seriously, it does have a nasty bark without some sort of muffler.

AND remember to take the plastic sheetrock pail covering the exhaust stack off BEFORE you start the engine...