Refreshing?
If your freewheel is a pre-hyperglide freewheel, it theoretically might be possible to disassemble the freewheel and reverse many of the cogs.
As the teeth on the freewheel wear, the spacing remains at 1/2", but the pulling side of the teeth gets angled so that the chain tends to ride high (and thus goes around a circle with greater spacing.
I've thought that it should be possible to mill the pulling side of the teeth back to the original profile. It would lengthen the slots between teeth, but that shouldn't affect performance.
Vintage freewheels tend to have blocky teeth, and should have plenty of material to mill down without significantly compromising the sprockets.
You'd need precision, and probably an indexing head, so hand filing probably wouldn't be adequate.