I've been replacing my shop lighting gradually, as bulbs and fixtures go bad, I've been replacing with T8 and LED's. I recently found some 4 ft LED shop lights at Menards for $34 . Although they are rated as the same,these seem to put out more light than the 4 ft T-8's.The LED's are rated @ 3300 lumens, but put out more direct light because they only light up on one side, not all the way around like a round bulb, and they only use 41 watts. The color level is 4200K, considered bright white. I have replaced all the bulbs on my machine lights with the 5000K LED floods, which almost has a blue hue. When I started out ,I was using the 2700K version, which was the only thing available at the time. These are more like an incandescent with a yellow light. When I found the 5000K version, I switched them out and used the others in the can lights in the house. Most of my machines had halogen lights, which put out a lot of heat. I burnt my fingers a few times, and it's not good when the bulb is exposed to coolant and oil.

I know there are kits to convert T12 to T8, and there are kits to convert T12 over to a single LED strip using the same fixture. The last time I checked, the LED conversion cost more than the complete shop light. The advantage is that the LED fixture is only 46" long and 2" thick, meaning that you could attach it to the existing fixture if you had to because you don't need any clearance for heat.