Originally Posted by
allout1
... my current riding bike has the 6 spd cassette and frame.
So, 6-speed Uniglide freehub? Have you removed the lockring and looked at the freehub body? Bolt-on or press fit. These are important things...
If bolt-on type, you can replace the freehub body with a modern Hyperglide replacement. Then, you're good. If press-on type, then you must modify the Hyperglide cog inner tabs to fit over the freehub body.
https://www.sheldonbrown.com/k7.html
^This page should help you.