You may need to spend some time at a Cadillac dealer's parts department. I researched some online sources that have some exploded views of the fuel system, but they are not very good. At least one supplier mentions the fuel pump including a pressure regulator, but they also list a pressure regulator for sale. Those pumps are pricey, if one ever breaks.

I think that lengthy fuel return lines from the engine have been eliminated on more modern GM engines. I believe that my filter/pressure regulator with a return fitting dates back to a '98 Corvette. It's now sold as part of a kit for LS engines, by Speedway and Summit.