Some GM chassis did have an electric pump in the tank from 86 on. How to tell if yours has one, there will be a pressure regulator on the right frame rail. It was made by Holley and the rebuild kits are still available for them. If yours has this regulator it would be wise to put a kit in it even if it's working as it will start leaking unless it has already been done. Just use the diaphragm from the kit unless the spring is too rusty, if it is, use the same color of spring from the kit or you will have to adjust the fuel pressure again. If that pump is bad the mechanical pump will have a very had time sucking gas thru it, and may not run when the engine is loaded.
