Question about other power hungry items on an EV conversion

[leitmotif]

Re air conditioning - I think you have left out a very important consideration ie where do you live?
Conversely here in Seattle cab heat and defrost are very important.

If you do not want to pay the bill for power brakes, power steering then do not get a vehicle that has all that stuff OR redesign front end and brakes to eliminate the need for motor - lot of agony etc. 
My conversion will be 56 Chev pickup no power brakes or steering AND I do not have to fool around with any computer control.

IF I were stuck with all that power stuff I would hook a motor to it and measure amps and volts and derive HP demand thus Kw
OR assume 5 Kw per unit size the battery accordingly and then take measurements.
Dan Bentler