Has anyone had any experience changing the final drive on an R80RT? I have an '86 that I resurrected from 20 years in some guy's garage. I'm a little surprised how fast it spins at speeds I need to do (80 MPH is 5,000 RPM). In So. Cal. you do this or get run over. Thinking of trying to fit an R100 final drive to bring the revs down. I'm OK with the power so that's not an issue.