I would not be to quick to blame the installer. While bending all four wheels is possible, I don't think it is likely. If the metal that locates the wheel is bent, yet the wheel is flat to the axle, other than looks it should be okay. As for balance, the 19.5s are heavy and heavy tires can be tough to balance. In my experience, I have had to re-balance most my tires after a few hundred miles.
It is pretty easy for you to tell if the rims are bent, or the tires are out of round. One way is to simply take the truck to a different shop.
I buy quite a lot from the internet, but not tires. Too much to consider for potential problems on big objects that cost a lot of money. I have also found with a little research and price comparisons I have never found a big savings on tires from the internet. With the tires in your driveway, you still have to have them mounted and balanced, pay disposal fee on your old tires, and probably limited on where you can take them for any warranty issues. If there is a problem like you have now, how and with who do you deal with it?
Wayne