Originally Posted by
paulrad9
Have you considered buying just a freehub body? I recently upgraded a set of old wheels from 7 to 10 speed by swapping the freehub body and still have the old freehub body.
The OP specifically stated that "
the freewheel body is not serviceable. It doesn't have any type of retainer, 10mm bolt or anything to take it apart."
But in a second read I'm noticing the the OP is talking about both freewheel and cassette for the same hub, which is frankly an impossibility.
So, to the OP: if you have a freewheel it can easily be replaced, and 7-spd freewheels are still readily available. And if it is a freewheel then it hasn't got a cassette that can be transferred to a modern freehub body by any normal means.