Quite a few years back, my DD was a 1990 Ranger EXT XLT, it had similar wheels (except with rivets). I went to Home Depot, bought a can of Polystripper, and went to work:) Put it on heavy, and once it starts bubbling, you can use a bondo squeegee to scrape the muck off.
The the polishing begins!!

:) We powdercoated mine, as my bro has the Eastwood setup.....and a word of warning, if you are going to powdercoat, getting the inside of the rim and the backside super clean is imperative, as we ended up having to strip & recoat two of the wheels due to all the junk on the backside of the wheels smoking & causing the clear powder to yellow:(
Best bet for cleaning inside/backside is a couple cans of Easy-Off Oven Cleaner & a pressure washer (and EYE PROTECTION is a must!!)
HTH
James