If most of it can be straight 1 1/2" od (non-flexible) exhaust pipe works good, if it needs a straight, 45, or 90 degree bend there is molded radiator hoses that have the right diameter, and the right bends in it, you just need to find a more friendly parts guy, who know his stuff, or will let you look at what molded radiator hoses they have on hand. If you can use straight exhaust pipe for most of it leave about 1" - 1 1/2" on each end shorter than needed so that it can flex. Another good source is http://www.mcmaster.com/#
they have just about anything you can ever need for anything you are working on (it's like the ultimate hardware store). Provided you can't find what you need from a tractor parts dealer. This post was edited by ptfarmer at 07:01:59 07/06/14.