Stock aftermarket pumps seem to work fine. Many stores can also still get a Delco part if you want it, but it will cost a little more. Also take a look online at the parts list at
www.rockauto.com, which has a very good display of the alternatives for your vehicle.
If you go aftermarket you might want to try a Stewart Components Stage 1 high flow pump. In the standard cast version its not much more than any other aftermarket pump, and will have a better impeller that provides a high flow rate.
Bruce