Yeah, I still think that looks like a conversion bushing, and I'm 100% sure it's a push-in one. Good pics by the way, I can never get my camera to focus for close-ups! :)
You could definitely put new Kluson-style tuners into the existing bushings. As I mentioned somewhere above, I found the holes in the conversion bushings a bit oversized for my locking Gotoh SD90s, but I am very fussy about these things. The bushings I have were from Allparts, they're not necessarily exactly the same as yours.
Alternatively, as the holes are 10mm+, you could take out those bushings and the whole world of cast/sealed tuners with screw-in bushings is open to you!
Removing the push-in bushings is usually quite easy. Gotoh actually supply a special tool, which is a small metal rod, narrower than the hole at the back but wider than the hole in the bushing - you could use an old 8mm drill bit as an alternative. Then just place the tool/bit against the base of the bushing from the back of the headstock, and tap (very lightly!) with a hammer. Once the bushing starts to move, it usually comes out really easily.
The only problem could be if the previous owner decided to go a bit over the top and glue the bushings in - they don't normally need it, but you never know. Then it might be best to leave them, or take the guitar to a pro...