There are no stupid questions when it comes to kit car building.
I'd suggest go for a ride in Steve's (sdm..1.6 K) and John Dry's (Honda type R) to compare. Both not too far away for you to compare.
Custom exhausts.
Found this.
http://www.jetex.co.uk/website/downl...-catalogue.pdf
Don't look too bad.
But don't Marlin do them?