I don't think they were coated from the factory from what I remember, and had what I would call a "raw" look. So bead blasting them would work to clean them, but I'd use something like walnut hulls to do it as that will clean but not change the texture. And, as Steve said, don't use steel shot to blast them.
I'm not sure polishing would be very easy. Again, this is my remembrance, but I think they have a texture to them that will require a lot of sanding/polishing to smooth out enough to achieve a shine.
But, I may well be wrong.
Gary, AKA "Gary fellow":
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Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI