I have a 68 Trade Wind. The original tanks was a plastic. It sits in a galvanized steel box with styrofoam supports. The steel box sits on supports that are bolted to tabs on the frame rails. I suppose you could do away with the plastic and make a stainless or aluminum tank. I purchased a replacement tank from Inland because the flange and the outlet area were cracked beyond repair. I had a buddy in the HVAC business make me a new box( made to original demensions) with some scrap galvanized sheet metal he uses to make duct work. I replaced the supports in the box with pieces I cut from 4x8 foam sheathing board I got at HD. If you need measurements let me know, I am not sure a 66 is the same as 68 but most likely it is.