IIRC, I've got a used vortech pump sitting in the garage as well that I'd let go pretty cheap.
One of the problems with the in-line setup besides the FMU junk, etc is that unless the pumps are matched for flow rate, one pump will outdraw the other one and usually cause premature failure of the pump that's doing the additional work.
Also, in regards to the 70 PSI statement, that's rail pressure after the FMU so it's not the pump that's giving you the pressure, it's the FMU boosting it up artificially. For my setup, I went to a 255 LPH in tank replacement pump similar to the focus pump, but it will work on return style cars.
Rick
