Before we kill the idea...

The PEAK usage is: 6 amps/690watts

Isn't that what's usually required to start the compressor?  From there
current usage drops.  It sounds to me like you would need a power reserve to
START the A/C, but you would be able to run it off the alternator after
that.

I have looked into the possibility of using a small RV-type A/C unit on an
air-cooled Westy while the vehicle is in motion through an inverter.  After
discussing the issue with experienced RV technicians, the folks who fix
these units, they said it could be done.

I'm interested in the outcome.

Chris.

'85 Westy, A/C functional