Its definitely the ballasts, not the lamps. The modern T12s work perfectly on any other ballast except those long AD LITES, Ive tried 3 brands too, (Sylvania Duluxe CW, Philips ALTO F40 daylight, and GE Watt Miser 34w) all exhibit the same erratic behavior. I will put em to the test with my multimeter tonight. Regarding the 35 fixtures/ballasts I discarded, they were in the roughest shape and the ballasts were mostly Mark III's and Bonus Lines, I run into these all the time doing office retrofits and can usually get you as many as you want. UniversalDave1 sounds good, the fixtures aren't going anywhere by June.

Yeah, sounds like more of a ballast problem. Even my preheaters will run F34s without going crazy, though I haven't tried it for long to avoid damaging the ballasts. The 25-watt shoplight lamps are a good suggestion; if those don't work, I don't know what will.

Try the 25 watt tubes.  If they wont fire, you have a worse problem.

I picked up some more T12s (including a 25w residential) on my way home, I Tested the fixtures with the long AD LITE ballasts, and heres what I got.
Parameters taken from ballast output (lampholders) while operating old Westy blackender (which operates normally)
Current- .50A
Voltage- 74v
*Parameters taken from ballast output (lampholders) while operating new F40T12 (Philips ALTO) operates terribly with extreme flicker so the values on the multimeter were constantly changing but it stayed between .43A and .50A and 66v and 70v
Values from the input (plugged into a Kill-A Watt using an old lamp (stable operation)
Current .56A Wattage- 67.3w

The new 25w F40T12 didnt even start, just kept preheating (blicking) continuously, the 34w GE actually started but caused even worse behavior than a full power F40T12, and the old blackenders that came with these fixtures work flawlessly. Figure out that one...

This surpasses my knowledge. I am surprised that you're getting .50A at the lampholder though; full power is .43A for an F40T12, so the current with the Alto seems more reasonable. Is the 67.3 watts at the input with just one lamp on a 2-lamp ballast? If so, that seems awfully high. My best explanation is that the capacitors in the ballasts are failing en masse, possibly from the years of non-use while the warehouse sat empty. Still doesn't explain why the old Westies behave fine. And I can't believe the 25-watter wouldn't even strike.

Maybe try running one of the fixtures with Altos or the new Sylvanias (40 watt only though) for a few days. The ballast isn't going to like it, but these ballasts don't seem to be of much use anyway. I just want to see if it will eventually clear up and run normally. Do fuse it or put it outside in case the cap decides to make a dramatic exit.

By the way, you're letting the tubes warm up, right? I just realized the Wisconsin cold will cause flickering with the new reduced-mercury lamps. If you've only been doing this in an unheated space, try a warmer spot.

The ballasts are 1-lamp and there is two in each fixture, each with a starter. They are dead silent when operating the old lamps, but hum when trying to run a new lamp. I too, thought the output and input current was very high for a single lamp ballast (I tested it numerous times on multiple fixtures.) Its just incredible how well the old lamps run, I barely even notice the 60hz flicker. btw, im doing all this testing indoors (70 degrees) not in the garage. Interestingly enough, I put a 110w VHO tube in just to see what would happen, and it actually ran less erratically than the new F40T12s, it still flickered but not nearly as violently as the other lamps. Of the 72 fixtures, about 50-60 of them have these old long (assumed AD LITE) ballasts, and the rest have a mix of 1960's Universal and GE. I will leave one fixture operating new lamps (the Philips ALTOs) for two days straight and see if the crazy behavior lessens. 

Two single-lamp ballasts in a 2-lamp fixture is a very odd setup. I assume they are still high power factor.

Worse comes to worst ill have to just remove all those ballasts and install rapid starts from another retrofit job, which sounds completely counter-intuitive as the whole reason I kept these was the fact that they were 4-foot preheaters, and preheat F40T12 ballasts are super uncommon, I almost never come across them. In fact, I can only remember one other time ive seen them.
One other thing I thought of, is that ive noticed some mercury vapor ballasts that have operated the same lamp for an insane amount of hours (well beyond its rated life), when provided with a new lamp, will never work the same again (bad flickering, arc swirling) almost as if the ballast has become use to running that 60,000 hour old lamp and it somehow changes the electrical characteristics of the ballast as to where a new lamp wont operate correctly. Maybe this is whats happening in this case. And ide be interested to know just how many hours are on those westy blackenders...

Yes all of these Sylvania fixtures have two ballasts mounts in the channel which will only fit the long design, which is the reason why I assumed these AD LITEs were the original ballasts

Please post some photos of the innards of the fixtures when you get a chance. This seems very unusual.  I have dealt with hundreds of old preheat lights and with the exception of one or two, the ballasts either work or they do not.  The exception is the very finicky F90T17 fixtures.  I got many of my lights from an old abandoned mill they were tearing down.  They had hung unused for at least 25 or 30 years and most still have their original ballasts and are in use on my farm.  The two tube ones mostly have General Electric "Tulamp" ballasts and the three tube ones have either a single 3 tube ballast or a "Tulamp" and a single tube ballast.  A few of the two tube ones have the "AD-LITE" ballast.  Two tube preheat ballasts can still be found, especially on e-bay.  Look up "205-TC-P" (Universal/Magnetek) and "8G1000W" or "8G1000" (General Electric/Valmont/Power Lighting Products).

Any 2022 updates for these preheat F40T12 shoplights?