Air tanks are air tanks. If it has two drains it is a dual chamber tank. Just one drain means it is a single chamber. The wet tank is the one the compressor pumps into and collects most of the moisture and needs to be drained every day. The secondary tank is supposed to be dry, but it will get a little moisture. The emergency tank the tank that supplies the brakes and should be isolated from the other side by a check valve. If you park the truck and hear a squeaking sound, it is the check valve bleeding into the other tank. If you go to a salvage yard just find tanks reasonably close to fitting they will work. If you can find aluminum ones that will eliminate rust. I bought my first truck with air brakes in 1964. Synflex nylon lines are the only way to go. Back when copper was all we had I was constantly replacing or brazing split or rubbed lines. And by all means use the push to connect fittings. That is all OEM has been using for about 30 years. I still have drawers full of compression nuts, sleeves, compression sleeves and compression seats that I hope I never use. And compression fittings for copper and Synflex are different.