Twinboat is right on, but if you have not replaced the fuel pump, plan to. If the pump is more than a decade old, it is not compatible with current "motorfuel". Even if that is, a the fuel lines (and most of the other rubber parts) are shot. They age out and there is nothing to stop that. Replace all the rubber fuel lines with some that is "alcohol compatible". If it does not say that somewhere, it is not. Also plan on replacing all the rubber brake lines and coolant hoses.
Mine is a 78 Cayo, and my sister has a 73 GMC. We have both been though this.