Jones

No different than connecting to the front or rear of the frame; it all goes back to the ground lead on the grounded battery. Just make sure your major components are grounded to each other; body to chassis, engine/trans to chassis, etc.

The only time grounds are a headache is when they aren't there and you have conductivity problems.
Cables getting hot and slow engine cranking, or lights that don't light are the most often heard complaints.
Or you'll see it when a circuit can't find a good ground and goes searching. i.e. With turn signals on, your dash lights also get bright and dim in unison with the flashing light.

Keep your wiring as simple and straight forward as you can. Use a wire gauge large enough to carry the load, and the shorter the run the less resistance.
A wiring job that looks like a basket of snakes is an invitation to mistakes in connections as well as shorts and crossfeeds.

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Jones
Sacramento, California

baby HEMTT