I actually just put 12 in the shop this week, just pull out the old ballast and wire the fixture to 110. I got them off of amazon
50watt output/24 watt bulbs. 5500-6000 KV delivered to my door for $25/bulb all in. They are many different specs/brands of LED bulbs out there to choose from. They are a whole lot brighter then my old T-12's that's for sure! I have a total of 12 2 lamp T-12 fixtures with 6 per circuit. I just replaced the lamps on the one circuit so it's easy to compare which is brighter. They do come on nice and bright right away when the shop is cold which is nice.
I have another bay beside the shop with t-8's and they are nice and bright too. As a t-12 replacement these LED's seem pretty good but at the current pricing I wouldn't spend the money on them to replace my T-8's.
I also checked the amp draw from these new 12 led bulbs at the circuit panel and the meter said about 1/2 of what the 12 florescent bulbs where drawing.