I broke the rules and did my led swap wrong. Everyone (box included) said I would need T8 fixtures to put them in. I just put the led's in the T12 fixtures, they fit, I read that the difference is the bulb to reflector distance. I did remove the ballasts in my car trailer just to lessen the overall weight. Every 50 lbs. I can leave out makes it easier to drag up the big hills.
I can run one bulb per fixture now if I want to because they are parallel wired. My shop has some of every kind of lamp T8, T12, LED with ballast, led without ballast, new fixture led's, led screw in bulbs two, or 3 on a porcelain fixture. It makes a busy ceiling though.