eBay item # 310372615814 . This item is a ge m250a2 with a 6.6 amp series ballast. Anybody know if GE still offers 6.6 and 20 amp series ballasts as an option?  Anybody know how an LED conversion would be done on a series luminaire circuit?

Hmm, I took a look on some of GEs spec sheets and I don't see any series options listed. In fact all of them also say "Metal Halide options not available after Jan. 1 2017" so I'd imagine they stopped offering series options too. a series luminaire circuit can be converted to LED but you'll have to install a transformer on each pole to convert to 120v multiple. As far as I know that's the only way to convert a series luminaire circuit to LED since they don't make 6.6A and 20A series LED luminaires or drivers.