We have been sending tanks to Moyer's Fuel Tank Renu 1-800-328-9550. They clean the tank, snad blast the rust out, meld in new metal where needed, coat the inside with a hard imperviuos plastic and coat the outside with a pliable black rubberized material. I am very satisfied. I think there process is a franchised type arrangement as I have heard of others with similar names through-out the rust belt.
I don't recommend using the epoxy/plastic fluids like Bill Hirsh sells because most people don't have the facilities to prepare the surface for the coating. I also warn against using known rusty tanks with fuel injected vehicles. While not as important on electronic injection as on K-Jet. I image 745 injectors are specially priced (bg).
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician