Yo, the pump you want is a 044 one made by bosch, what the majority of modded cossies use, the 044 relates to the last three numbers of the part number, this together with a proper rewire usng a feed direct from the battery and a switched earth and relay controlled by the original wiring. You can buy the looms on here/ebay or get a diagram and do it yourself, i bought the loom as I wanted i to look neat and it looks more "pro", plus i couldn't be arsed making it myself.
general rule of thumb is 4x4 manifold upto 400 & 2WD beyond if i remember correctly, also 4x4 is allegedly better for torque which is important, though some may be able to elaborate on this. 2WD manifold is 2 piece, 4WD 1 piece, 2WD has a hanger joined onto the head, 4x4 doesn't. That should cover it 4 now. IMO i'd slap on some siemens blacks and a better chip, thats what I intended to do but given up 4 justnow.