The B&B muffler body is around 2-11/16" x 1-3/4" x 15/16". The stingers are 1" ID. I think B&B makes several different sizes, but these measurements are typical for the small gassers.

The Rascal firewall height is 7". The width is 4-5/8" on the outside and 4-1/4" inside the two extensions. The cowl obviously tapers toward the nose and so is kinda hard to take measurements.