Ahh thanks for the info on the LED cobras. Yeah that Universal ballast was nice but there's some cheaper two lamp ones still on eBay. I've seen the T17 and the Magnetek preheat ballasts a while back but it's nice to know they are still for sale. Maybe if I can afford it, I'll try to see if I can get a Magnetek preheat ballast and one of the newer T17 ballasts. Then I just need the lamps, starters and starter sockets to make myself a T17 fixture.
I didn't know about the Advance F40 preheat though, the postal zone on the address (as opposed to a ZIP code) suggests it might be from the 60s or earlier. Also you can see that the Advance preheat wires up exactly like my Universal 203, without the lead lamps starter going into a starting compensator. I'm not actually sure why they had two designs at the same time though. Both types seem to be lead-lag type ballasts.
Also I'm not sure how much shipping will be but there's someone on LG selling a bunch of
F90T17 lamps for 175 a case which is a pretty good deal if you need a whole case. According to Aaron's pics he also has other types of rare and interesting fluorescents.