You might do better finding an inverter and battery bank with enough
capacity.  The generator is going to require you to be able to maintain
quite precise control over the speed of the engine -- you might be able
to use a cruise control to make this happen (sensing the speed of the
generator pulley instead of the wheels), but I'm sure there would be
other issues ..

If you do decide to go with an inverter, you could also install a bigger
alternator if you need more power.  One really nice thing about using an
inverter is that you won't have the sound and smell of your engine.
(Until you have to recharge the battery, at which point you'll either
need to drive or find a way to speed up the engine while the car is
standing still.  The alternator will need to be spinning faster than
idle to put out a significant amount of power -- though if you could
steal the clutch from your AC, I suppose you could put a small pulley on
a second alternator and get it up to operating speed while the engine
idled.  Though I don't know if the ECU would supply extra fuel to keep
up idle speed, of if you'd end up stalling the engine with the alternator
load.)

Depending on the amount of power that you need adding some deep cycle
batteries (and you want deep cycles if you'll be drawing them down
signifcantly, and care about their life) to supply the alternator.  You
could either mount the batteries semi-permanatly or in a removable box.
Just make sure that you've got it really securely attached.  A loose
battery in a car is a really unpleasant thing, especially in a crash.

Doug
--
Douglas L. Urner <dlu@canishe.com>  Port Orchard, WA   +1 360 769 5565