Patrick's sells an expensive, but very nicely made stainless-steel dual-exhaust/muffler kit for Fenton dual-exhaust headers.
The sound is distinctively "throaty" (on the 1960 261 in my 1954 Suburban).
Too loud for me.
My guess is the cab noise would be more civilized with a pickup cab.
Picture is attached below.
Here is Patrick's catalog. Scroll way down to CHEVY DRESS UP PARTS."1947-1955 1 SERIES 1/2 TON CHEVY OR GMC PICK-UPS
Stainless Steel Exhaust System, complete for use with Fenton Headers………………………………………$675.00 Includes head pipes, muffler, tail pipes, clamps and hangers, complete. Exclusive side-by-side, "shotgun" tail pipes. Fabulous sound, awesome appearance. (long-bed GMC 1/2 tons require extensions. Optional $59.95 w/clamps)"
If your header "dumps/drops-down" like the Fenton header, that set will work.
(forward exhaust-pipe angle drops about straight down, and the rearward exhaust-pipe angle slants to the rear)
If you only want the muffler, send me a Private Message - I will measure the diameters of the pipe fittings. I think they are probably 1.5" diameter.
That two-in/two-out muffler is loud/throaty. The pipes exit behind the driver's side rear wheel.
Be fore-warned about buying directly from Patrick's. It seems that he has become quite unreliable.