[blitz355]

bearings you can buy in 0.0005" (or less) increments from some suppliers on ebay. its cheaper if you can buy them already set up correctly of course, but if you need to change existing blocks, it should be fine. 20mm blocks take 1/8" balls (yes, not metric). 0.1255 should get you medium preload.

Is medium preload recommended? I think the sbc bearing he uses, like he said k1. K1 according to sbc data sheet is normal, and k2 is "light".
Good to know that you can find them on ebay, do you search anything specifically or just "ball bearings"