Mike
Had quick look at the spec on the pump, I think it would be better as a belt driven pump, then a direct drive, so you would need to check rpm on your engine IE does it run fast enough for this.
Mine be worth speaking to Speck re this.
As for the output, 40lt 2000psi is ok/good, I have a 27lts 3500psi and it is easy enough to control, just ease off the pressure according to the surface you are cleaning.