So what keeps failing?Are the boosters rusting out?

No, brakes no longer work. Wonder if water is getting into booster and causing brakes to fail.
Ford had issues with windshield wiper motor because of where it is located and the water. Wondered if you had heard of any problems with Chrysler's boosters because of where they are located.

So you lost the power brakes and the brake pedal is very hard now?Have you looked at the master cylinder to see if it's leaking fluid into the brake booster causing them to fail?Also what brand and where are you getting boosters from?

Will check out the master cylinder. The second booster was from Triple Nickel a salvage yard. The one I just purchased was from Autozone and is a Cardone Remanufactured Booster.

Old booster full of water and connections rusted. New Booster didn't come with seal and there wasn't one on the old one either. Any suggestions?

Use some clear silicone to seal it up so then water doesn't come in you can try that.