In case you are interested, our muffler that we use on the Cup cars measures 14" total length, 10" body length and 4x7" body.
We can make it in 2, 2.25 or 2.5" inlet/outlet to match up to whatever exhaust diameter you are choosing to build with.
The cost of the Muffler alone is 140$CDN +shipping.
The website is still under construction but here is a link for you to get a bit of an idea:
http://cortekexhaust.com/mufflers/47-series/