The guts of the pump are only part of the equation. The resistance of the suction path is also quite important. The turbo pump is all smooth wall tube. The truck pump has a long section of rough wall casting. The latter will be markedly more inefficient, since both rely on ambient pressure on the surface of the oil in the sump to "push" the oil to the gears. This is a very small force, compared to the positive displacement of the pressure output.

I deal with this every time I design a pool pump system. I have to minimize the number of fittings in the suction piping, and use large enough pipe diameters in relationship to flow volumes and velocities.

I can't give you the exact effect, because I don't have a value of C for the casting and the tube, but the math is all in something called the Williams-Hazen formula ( at least that's the one for water - valiable viscosity oil may have a different formula).

The pickup mod ification is not all that difficult. Proceed thus: Place a wad of modelling clay in the truck pan under the pickup location and with the truck pickup installed, bolt on the pan. Measure the pickup-pan bottom clearance in the mashed clay. Install the turbo pump and pickup, and repeat the measurement. The diff between the two is the distance you need to extend the turbo pickup. Cut off the pickup from the pickup tube in the lower vertical section and weld in an extension tube of the calculated length. Pressure test for leaks in the weld, as any air leaks will be really nasty for the engine.