ok so to answer your questions,
1- the exhaust I found on the side of the road and it looked way to good to pass by, from the tag i can tell it was from a 400cc suzuki street bike? Not sure but at a low idle it sounds like a quad.
2- The indicator is from a 70's suzuki 125 enduro and thought it looked cool and it works but, my transaxle doesn't have a neutral safety so i used the the clutch safety switch to indicate "neutral"
3- As of right now i would guess it will do 30-35 km/h with a 8" front pully and a 8" rear, before with a 8" front and a 4.5" rear i clocked it over 50k but hard to manage with the stock steering lol its a old briggs so i just repositioned my throttle cable to control the butterfly in the carb, with a separate choke.