I got given a Rayleigh Scorpio unsure of exact age (late 80s or early 90s), and I am currently fixing it up. The issue is that its need new wheels as the current ones have a very poor braking surface and poor overall condition. Is it possible to place a 6 speed cassette (Shimano SIS MF-HG20) on a wheel that is not compatible with 6 speed. The wheels I am thinking of buying are Shimano R500 or RS10, the website that sells these states that there compatible with 8, 9 & 10. What process if any would allow me to use my existing cassette on these wheels, and would it be appropriate/safe.