Sam just contacted me off-list about the B-8 (since I've written several posts about mine). I replied to him directly, but am repeating my answer here, in case anyone else might be interested:
Sam,
I haven't printed 35mm for years, although I do have the flat lens board for that size. The usual focal length for 6 X 6 is 75 or 80 mm. According to the late Harry Taylor, who ran a wonderful Omega website until his death a few years ago, an 80 mm lens works fine without a supplementary condenser, but a 75 needs the long discontinued "thin" supplementary condenser. There is also a "thick" supplementary condenser for a 50 mm lens. Both supplementary condensers come up on eBay from time to time. Harry sold new thick ones that he had made, but I suppose those aren't available anymore. I have both–the long-discontinued "thin" condenser took a while to find. I suspect you could skip the supplementary condenser and it would be fine–why not try it with your 50?
I never made prints larger than 11 X 14 from 35 mm, with a 50 mm lens on my B-8. IIRC there was lots of room for cropping. An 80 mm lens almost lets you make 16 X 20s from 6 X 6 negatives; a 75 works a little better, but both leave you with no room to crop and very wide margins. BTW the only REALLY good 75 I know of is the old Kodak Projection (or Enlarging) Ektar, a 5 element lens that's the equal of more recent 6 element models.
I use a 60 mm WA Companon lens now to make 16 X 20 prints from 6 X 6 negatives. I use it with the flat lens board intended for a 50 mm lens and the supplementary condenser intended for a 75 mm lens, but that condenser probably isn't necessary. With the wide angle lens there's plenty of room for cropping. I think I could make 20 X 24s, if I had room for the trays in my tiny darkroom. !6 X 20, and even 11 X 14 trays require a tray ladder to fit.
As far as lens cones go, I use a 1 1/2" on for my 80 (or 75)mm lens and a 2 1/2" one for the 105 mm lens I occasionally use for 6 X 9 negatives. I don't think there's any advantage in using a 105 (or 100, or 90 for 6 X 6. I THINK lens cones made for a larger Omega D-2 also fit the B-8 (and cones for the earlier "B" model enlargers) also fit. AFAIK the lens discs, that hold the lens to the cone are all the same.
With Harry Taylor's demise the Omega authority is KHB Photografix in Canada:
http://www.khbphotografix.com/omega/
They may have some old parts in stock, but they're usually much less expensive, and fairly common, on eBay, although you'll usually need a standing search and some patience.
If you buy the B-8 get a few extra bulbs. They're still made (and new old stock ones come up frequently on eBay) but the have an odd base (the same as Beseler B 22s and older 23Cs). FWIW I've had my B-8 for >10 years and haven't replaced the bulb yet, but I have several extras, just in case.
I really like my B-8 and think you'd like one two. You also might want to consider a 4 X 5 D-2 (similar, but about 1/3rd larger) if you have room. The comparable Beseler model is the 23C, which is also good.