Can you use led bulbs in them?

As Bogieman said. You can easily convert T-12 fluorescent fixtures to LED. Just get 4 foot "Double ended" LED tubes. Do not get "Single ended" tubes which requires more advance wiring, since power goes to one side only. For Double ended tubes, Cut out the Ballast. All wires from one end connects to hot, other end connects to Neutral. Check online videos for help.

There are definitely LED T-8 lamps that will work with electronic ballasts. However there appears to be no advantage to using the ballast as the light output will be the same and the ballast will actually use more electricity than just removing the ballast and wiring straight 120v. I have just purchased 6 5K led 4 foot bulbs and installed them in my old 4 ft florescent fixtures. They are fantastic, are brighter than the florescent lamps and there is no ballast to worry about. I need 3 more fixtures, that is why I am here pricing them. I am going to get these and immediately remove the ballast and wire up the leds. Easy to do. The lamps are about $9 a piece, so the florescent is cheaper, but the led light is brighter. Sadly, I had to order the led bulbs, Lowes did not care them.

No. The LED bulbs are not compatible with the ballasts in common fluorescent light fixtures. I would use the standard fluorescent bulbs that were designed to be used with your fixture.

To my knowledge there are no led bulbs made to fit this type of fixture.