FWIW, the 1" collet that came with this one appears to match dimensions listed for OZ32 collets. Of course, the only source I can find that will ship to US that has an inch set of collets, is on backorder... sent them an email asking ETA for another set available... It's either that, or really go with the ER40 adapter..
I did start the initial disassemble of the B-600 head yesterday. Not quite as bad as I had imagined inside. There was some moisture in there, but not too terrible. Any amount is too much anyway, so... I did however notice, prior to disassembly, that if it sat for a couple days untouched, rotating the shank (#40) was stuck in place until it "broke free" (by hand rotation force, nothing wild), and felt smooth after a couple back-and-forth twists... Hopefully that doesn't spell doom for the larger bearings... Once access to inside was gained, I coated everything with light oil while I wait for a snap ring plier set for further disassembly.
Just checking it now (since yesterday afternoon) it locked up again, but rotating again after rotating back and forth. Not optimistic for the bearings... Maybe by some luck once disassembled, they'll clean up with solvent, and once greased again, will be able to sit without locking up... idk... no idea on cost for those, would likely replace if not too expensive. Maybe something like evaporust might work, no idea, never used it.