AC50 and medium sized cars

The AC50 seems to have the highest profile of the AC Motors but I read varying anecdotal reports of its capability around hills. Chinese BLDC motors are looking very promising as an alternative.

On my commute I have a hill climb that has to happen. My car is a BMW 318ti. I am doing all my calculations at the GVMR 1555kg just in case.
The hill is a 4.6 degree angle (8 percent incline). I have calculated this to require 30-35Kw, and as it is 2km I will need to hold this for 90 seconds. If I do 1:1 through a transmission to the 4.44 diff then 3000 RPM will do 80km/h - sounds perfect. (Side question: I haven't decided whether to modify the auto transmission or put in a two speed transmission yet, but understand the former may add significant losses - any idea how bad?).

Either way, is this motor up to it? The chart says it can do over 40Kw at 3000 and at that point still has its 150 maximum torque.
http://hpevs.com/Site/images/jpeg/power-charts/pdf/ac50_102v_650a_metric.pdf

However people quote 50kw as its peak performance. So is this graph all peak readings? If so, how long is it reasonable to expect a motor to operate at peak for? And what if one added a water cooling plate to this motor (and to the controller), what impact would that have?

Richard