Which Nelson? from 12 er's
 

Any 12 er runnen a Nelson muffler out there?
I would like to know which one to order from someone with experiance with these mufflers on a 12v.
I'm not doing anything fancy, just dropping the orig muff & cat and slipping in the new one with all the original piping except for adapter pipe.
It seems the #86131M, 51", is very quiet which I could live with. But then someone said they used a ?#MO85171, 41" which was a little more throaty.I'm sure the # is #85171M.
Does anyone know if this is a true part # for Nelson? And does anyone know about this 41" sound? I still want the truck to sound like a truck not a Caddy!
Thanks- Trent