Mount the controller some where safe where it wont get knocked or damaged.
You don't need to use the AC override
12v power direct to battery or if you want it neater run it into the fuse box and bolt it to the main power there
12v ignition you can pick up in the fuse box as there are quite a few switched supplies in there
Earths for the fans on the chassis, there is a bolt behind the battery on the chassis leg, use that
You can also mount the controller on the side of the chassis leg
You will need to trim the battery tray slighty around the fans