KH piston dust seal fixable?

Well, I would say that those are even more so desirable (possibly).
If it were me? I would offer what you have up for trade for exact same that will work on your 68.
You have something hard to find, dont "get rid" of them until you have what you need!
Oh, $140 at RA? I would be all over those...
FYI
Be very careful these days in what you think your getting from Rock Auto in the way of prices for the calipers they have for sale.
Those calipers go in an out of stock faster than babies go thru diapers.
You may think those prices are cheap, but if they don't come with the caliper hard lines, they are now costing in the $60.00 dollar range to get.
Then the cost of pad hold down clips, more $$$$$$.
Then the cost of pads, of your choosing.
Also the shipping charges these days are thru the roof, adding onto the cost.
These calipers are not cheap to rebuild, or purchase in this day and age, sad to say.

The calipers that i currently am working on, the replacement, rebuilding parts have gone up substantially, since the last pair that i went thru.
Sad to say, my next selling price, will be with a price increase. Can't do anything about it.
Jim V.
hemi71x