My plan was to use the "fuel filler" area for getting AC power to the battery charger. Because the body panels are plastic, mounting options for the receptacle are limited. The only real solid place to attach a receptacle is a single "speed clip" attached to a metal bracket in the upper right corner (where the original gas tank filler pipe was attached).
I cut a crudely-shaped piece out of some scrap aluminum sheet (1/8" thick) and cut a hole in it to accept the body of the receptacle. I drilled and tapped 3 holes situated around that hole that matched the mounting hole pattern in the receptacle flange, and then drilled a clearance hole for a #10 machine screw to mount the aluminum piece to the metal bracket's speed clip. Once mounted in place, it looks like this:
It's an L14-30 receptacle. I chose the L14 style because I wanted a turn-lock style (as opposed to the dryer style) for a more secure connection and I decided it would be a good idea to bring in a neutral line in case I have components on the car that run on 110VAC. Like, for instance, a little trickle charger for the accessory battery, or blanket-style battery warmers.
So, from this receptacle I ran 4 10AWG wires (2 black wires for the hot lines, a red wire (with white electrical tape wrapped around it - I ran out of white and had plenty of red) for the neutral line, and a green wire for ground) through the body at the top of the inner fender wall and into the rear electrical enclosure. Here's a view from behind the receptacle:
Here's a view of the fully-wired rear enclosure:
I have the power coming in from the right side and leaving the left. The blue and red wires are the AC input to the Zivan NG3 battery charger. There is an additional green wire that connects to the chassis and serves to tie the chassis ground to the AC power ground line (earth) while it's plugged in. Two of the small black wires connect the AC power to the Primary AC Interlock Relay in this enclosure while the others run between this relay and the other relays in the relay enclosure in the engine compartment.