With the exhaust I bought a pair of used turn-outs off Ebay. Don't know what manufacturer, but just ground-down the tips to make 'em fit. Love 'em, sound real beefy and look great (in my opinion). I have 'em mounted with a bracket bolted onto one of the rear passenger peg holes.
Absolutely. If your bike is already an '86 VT500 then it'll be even easier. All you'll have to do is rip it all apart, and cut & grind the pan down to your desired size/shape. Then re-upholster, or have it reupholstered.
The only reason I didn't use my OEM seat is because it was in such good condition that I wanted to put it up on Ebay to sell (which is up for sale now) instead of cutting it down.