Crazy as this sounds I just bought a replacement muffler on Amazon. It is coming from Truckpipesusa.com. Cost $288 plus shipping and tax about $350.
Umm I don't need a muffler...just the correct pipe to exit exhaust gasses out the side cut out in the body.
Truckpipeusa will likely have what you need.
Just remove that 45" pipe with a 90" that will line up with the relief cut in the rocker panel.
I would remove that short pipe first. Loosen the two bolts on the band clamp to remove . Measure the diameter of the muffler exit pipe. Purchase an “L” shaped pipe that is obviously longer in both dimensions with an ID that will fit over the muffler pipe. Hold the pipe up beside to accurately mark where u need to cut the pipe to length on both dimensions. Use a new band clamp to install. U may need to install an additional hanger for the extension pipe.