That's probably not a good idea. The mechanical pump would have to pull fuel thru the electric pump and they're not made to do that. Why do you want to run both? What is the combination? Is it street/strip? If street-only driving, run the mechanical. If you want max power for the strip, run the electric. Either pump will work fine for the street, just make sure that they're rated properly for the amount of fuel you need to flow and use a filter! Good luck!