I have a 1972 Olds Cutlass Supreme Convertible. It has a 350 Rocket engine with a 4 barrel carburetor and single exhaust. I'm replacing the fuel tank. I ordered a 20 gallon tank but the neck is too short and the back doesn't bolt up with the same bolts. Any suggestions

 

Where did you get it and how did you verify its fitment before purchasing?

 

Provide a Part Number and/or a reference to a link/URL which demonstrates which fuel tank you ordered/received so we can possibly assist on addressing suggestions. It's possible they sent the wrong one?

 

Also keep in mind that the bolts will ALWAYS be tough to get started. That's just life. The straps need to stretch to hold the tank in place. Any minor bends or slight misalignment of the tank in the straps makes it nearly impossible to get the bolts started. I've often had to use a floor jack with a large piece of wood to raise up on the tank enough to get the bolts started. As for the filler neck, as others have said, tell us exactly what you ordered if you want useful answers.