I had already rebuilt this transmission, but didn't replace any bearings at the time. Here, I've dismantled this one only far enough to replace the 6305 bearing on the mainshaft.
I think I'll just let the pictures tell the story here.
One note on the 6204 bearing fitted earlier. I found this caused the secondary shaft to bind a little. I removed the transmission and investigated. At first I thought the bearing hadn't seated all the way into the block. Checked that. No different. Looking at an old bearing compared to the new the old bearing has more of a rounded shoulder than the new one, so seats .10 mm deeper.
Rather than pull this bearing back out and chamfer one edge I decided to remove the .10 from the thrust washer that fits against this bearing. Binding fixed - but only after having the transmission in and out about a dozen times for test fits.
I have more of these trans to fit bearings to when they are fitted to motors. In future I'll bevel the bearing before fitting it. And before removing the bearing seals.