520 horizontal exhaust

If the muffler is shot, but still in one piece, build a wooden fixture that clocks the muffler flanges in the correct position and cut the center section of pipe off with a saw. I used a 4" dia truck exhaust pipe to replace the center section of muffler and had a welding shop weld the pipe onto the cast flanges while in the fixture. If it's like my 50, the flanges will be smaller than the 4" truck pipe, so save the weld beads on the cast flanges at each end of the pipe to increase the OD of the flange so there's less gap to fill when welding the new pipe.

On the tailpipe, I used the sketch in the parts book as a starting point and reverse-engineered a pattern and built a pipe-bending fixture on a sheet of scrap plywood for the muffler shop to bend a new 2" piece of exhaust pipe. The whole thing took more time than money and set me back about $75 in materials and labor. I now have a new exhaust system and it sounds good! Hope this helps.