Under the dash on the driver side ( on side not firewall ) there is a small ground block with 6 or 8 spades. For 12v power, use the block on the firewall under the hood, just to the left of the glow plug relay setup. For 12v ignition controlled, there are empty spades in your fuse block under the dash. Check voltages 1st as there is one empty spot that is 24v.
There is no need to wire anything straight to the batteries.