Lots of studies comfirm that ideal pipes for these 216 to 235 ci engines for backpressure and gas mileage work best with under 2" pipes, 1+5/8 to 1+3/4" ideal if you can find the pipe. And place your mufflers back as far as you can without crossover. I like the brockman mellotones steelpack mufflers, you can get them made any length. Have also used smittys, borla, flowmasters, jeep etc.
