Re: custom exhaust
1/2" and 3/4" EMT (steel electrical conduit) works great. Benders are cheap and once you get the knack of getting the bend where you want it you can do almost anything as far as an exhaust system goes. The bend radius is a little longer than I'd like but with some practice you can reduce the radius by moving the pipe in the bender as you go. There's no need for sand or heat. An added plus is if you use new conduit the galvanized coating will take a nice shine with a little work on the buffing wheel and some compound. Napa sells a silver high temp engine rattle can paint that will withstand the exhaust heat even right at the cylinder/flange.
Here's a couple of pipes to give you an idea of what's possible.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"