On (2) W150 I did 2.5" exhaust pipes. Passenger Side pretty much straight back with a slight offset around the transfer case. The Drivers side went back and crossed over to the passenger side behind the transfer case then ran parallel to the other exhaust tube. one had dual turbo mufflers side by side, the other used a dual 2.5" inlet, single 3" out baffled muffler. I don't recall the muffler brand, it was a smaller brand name, and it may have actually been a 3" in, dual 2.5 out installed backwards? I sounded good with a warmed over 318?
Because these were the trucks with drivers side fuel tank, the muffler(s) were on the passenger side. The '84 RamCharger had the rear mounted 35 gallon fuel tank, so I think there is room for a muffler on the drivers side?
If you are using that rear mounted fuel tank, I would modify it to limit fuel slosh (Fuel cell foam or baffles.)
I had about 20 gallons of fuel in my tank, and took a corner a bit to fast, and the fuel slosh kicked the back end loose, then when I went to correct, it sloshed the other direction and spun the 95" WB truck around. Rear tire caught a curb and tipped the Ramcharger over onto the side.

I think the Muffler Brand used for the dual inlet single exit was IMCO? When I looked it up, it seems to be Cherry Bomb?