Did Sylvania ever make t12 ballasts? I have a 2x40w GTE fixture that came with a cge ballast, a 17a240E. I still have the fixture, but I needed that ballast for my den light.

They made "Dua-Lamp" 2x40 preheat ballasts in the 40s and possibly 50s, magnetic RS and Slimline ballasts during the 2000s, and they currently make Quicktronic electronic ballasts for T12 lamps. I'm not aware of any others.

I think sylvania only made fixtures when they were GTE sylvania (excluding 40's, 50's, maybe 60's)

They made the HF-100 during the 40s when they were Hygrade Sylvania.

A full line of T12 and other ballasts was made by Sylvania.  Recently I scanned in an old 1966 Sylvania catalogue for the French market, and this gives quite a good overview of their ballast and fixture line.  It is not the complete range because only some types were offered for the EU market, but I believe that what is included there should also have been available in Americas.  A few types perhaps not though - at work we still have a lot of old T12 8' HO and VHO fixtures in use, and the ballasts inside these, although marked Sylvania and produced in 1968, are also marked as made in France.

http://www.lighting-gallery.net/gallery/albums/userpics/10343/normal_220_V___3000_W_E_40_Cu_CLEAR_IMP_I.jpg