BACKGROUND: I need to replace the gas tank on an '87 XtraCab Long Bed 2WD Pickup. Mileage 220K miles. My Owner's Manual states I have a 13.8 gallon gas tank. This agree with the most gas I have ever put in. My model code is RN70 which does not show up in the VIN decoders other than to tell me I have the 22R engine with the mechanical gas pump which I already new. PROBLEM: When visiting various parts sites online, the RN70 model code does not compute. Examining fuel tank options for 22-R, all fuel tanks online are 17 gallon capacity. I am trying to determine what is my best option here - just try and fit the 17 or what? Will it fit? I was anticipating buying new straps at the time I buy the tank. Are there any unique gasket and hose issues? Also - what about a new fuel gauge sending unit? Can't seem to find one that is OEM or stock replacement other than generic units. Don't want to buy from dealer. Additional info: I have a new Airtex mechanical fuel pump with gaskets in a box as I am still running on the factory original and believe the original has started to malfunction. Intended to replace but the tank now comes first. All help appreciated in advance.