dovebiker on "8spd Freewheel on 6spd wheel"

Road wheel or MTB wheel? 6 speed road wheels were generally 126mm OLN whereas 8 speed are 130mm - you need to fit a longer axle and probably re-dish the wheel to make this work. The reason the 8 speed freewheels didn't catch-on is that they put a lot of load on the hub bearings / axles - on a cassette hub the bearings are more widely spaced.