Thank you all!
David, I saw your story. That's some nice work. Do you happen to know the thread on the back nuts? As I'm in the US my lathe is for standard threads but It's my understanding that I should still be able to get "workable" metric threads at least in a few combinations. I could then (maybe) thread up an aluminum bar and do the face truing on my nuts one at a time?
John, it looks in the picture like you used some sort of cutting tool in a boring bar holder and basically "drug" the key way in? My internal plastic spacers are going to have to stay, I have no way to make new ones right now and if I never have to take the head back off, it'll still be too soon but I'll most likely do the back spacer out of aluminum. I do like Davids notch idea. I could cut that with a Dremel too as I'm thinking it doesn't have to be very precise.

Bolstered by reading that this wouldn't be too bad I went last night to the local auto parts store and bought the two bearings! Timkin branded, one made in France, the other in Poland.
I bolted my shaft vertically to my other work bench and had at reducing the diameter of the shaft for a sliding fit for the back bearing. I had to do it old school with sand paper and shoe laces but it seems to have come out darn near perfect. I can just slide the bearing on. If it's a little cocked it won't go... at all, but get it square and it slides on and will move fairly easily but not fall on. That took hours!
Which leads to this question... Do I have to do the same for the front bearing? I think I read somewhere that it is actually better if the front is still a press fit?

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EDIT: I ended up doing the front of the shaft for a very tight sliding fit.