I received a Park 370 Outrunner Brushless 1080kV motor as a birthday present.  (wife can't stand the smell of caster)  Does anyone know if this will power a 1/2 a sized pathfinder?  If so, any ideas on battery size and esc that will work with this combo?  I assume a z-tron timer will be needed as well.  Any help in this regard would be greatly appreciated.

The 1080kV means that with 12V, the motor would turn 1080 x 12= 12960 (~13k) RPM with NO prop (this is ignoring any friction in the motor bearings). 12 V is a little less voltage than a fullycharged and unloaded 3 cell series LiPO. The maximum power delivered by the motor occurs roughly (because of any friction) at 1/2 of this maximum rpm, or 6500rpm. You always would like to run the motor above this rpm so that when you pull the nose up and the rpm drops (I am not assuming you are running in governor mode on the electronic speed control (esc)), you can have more power delivered to the prop to minimize the rpm drop. Also flying at 70% of max rpm probably keeps the current draw down.I note that the current draw is max at 0 rpm and minimum at 13krpm (-0 if no friction). Torque is directly proportional to current and is maximum at 0 rpm---where you could burn out your esc if you stalled the prop!  The delivered power to the prop shaft is zero ar both 0 rpm and max rpm. The power burned by the battery (current * voltage) is max at 0 rpm (all your precious energy goes into making heat) and 0 at max rpm (because the current is zero).

Anyway the motivation for all this is that if you are flying at 70% of max rpm, this is 9000 rpm. That is a relatively low rpm for 1/2a stunt so I think you will need a pitch in the 5-6 inch range to get the plane speed in the right range. Choosing the diameter depends on the how much power that motor is rated for. The manufacturer probably has recommendations. Too big a prop will put the rpm's down too low, too small a prop will give high rpms and little power delivered to the prop.

It may sound complicated, but this is trivial stuff compared to understanding the power curve of a 2 or 4 stroke engine. 

I think Alan has a pretty good starting place there.  Go to your Electri Calc and find a prop with 5-6 in. pitch that the motor can turn at 9000 rpm.  If it's anywhere over 7 in. it should at least fly the plane.  If it actually pulls 12-15 amps at 10-11 volts(120-165 watts) that should be plenty of power for stunting.