I agree that it is time to inspect what you've got. That means climbing the mast (hard, since I like to use both halyards with one as a backup), dropping the mast, or looking at it from a neighboring tall structure.
I also had to replace the sheaves on my Catalina 25 for similar reasons. Interestingly the original sheaves on my 2 year newer Pearson 28-2 were in excellent shape. I lubed them and put it all back together.
The hardest part is finding sheaves that fit well. From what I've seen Harken, Schaefer, and Garhauer don't have them. Of course your Ranger 23 could also use a custom masthead with different sized sheaves than the standard mast.
Ronstan has this, which may easily be modified to work (though it is a bit small):
RF1751 |Ronstan Sailboat Hardware US
This is another candidate to evaluate, and would last longer:
RF40000HL |Ronstan Sailboat Hardware US
Neither is in stock at Fisheries Supply, which makes it harder to evaluate them for modification.
If only the center hole on your sheaves ends up being worn (the outside perimeter is okay) and depending on the design, I may be able to rebore them for you and add a brass bushing. I have a lathe in my basement workshop.