Hehehe.. I like the shape of the curve of the Little Giant pumps in that chart.
As for calculating the head pressure, you can do it, but as the pipeing becomes more complex (ie, gradually curved, sharp kink, resistance based on flow rate (differential equations, etc)) it becomes harder. I had a page linked one time that gave formulas for figuring out head pressure based one 3 things:
1) Type of material used (different material have different flow resistances, everything else being equal)
2) Diameter of tubing (or pipe)
3) How many bends or 90 degree angles you have.
So, if you have a mix of diamters (think tubing -> radiator here), materials, curved pipe, etc.. it'll be hard to calculate but you can get an idea. Use altavista, and search for calculating head pressure.
Rich W.