Sounds like a great project!
One thing to remember is that when you're stopped at the lights or something, your motor will be stopped, and so the A/C and the power steering will be stopped, too. A separate small motor could be better, if you're in traffic lots - though even if you're going slow over rough terrain they wouldn't be going very quick.
I look forward to reading more! Sounds alot like my project, only I'm aiming to use an old Brumby/BRAT ute
