so, i posted a thing a little while back where I had a leaking ballast, it still worked fine and did not run hot or anything, but it was indeed leaking, so i decided to go ahead and replace it, but of course if I am replacing a ballast and I am able to put in a preheat ballast that is what I will do. they are normally pretty expensive because people think everything old is worth a fortune, so I was pleasantly surprised when i found a NOS advance preheat ballast for one f40t12 for $15 shipped. so i jumped on that and i got the ballast today and went ahead and converted the fixture to preheat. of course when trying to fit the starter socket i drilled the holes opposite of how they needed to be, so now i have 4 holes, but other than that everything went smoothly.
https://www.youtube.com/watch?v=BRVH5_MJIwA