Locally Grounding vs in harness

Hey all, I am about to begin building my wiring harness(es) and have a question on grounding. My ecu and relay system is centrally located in the footwell of the car. I have an electric fan for cooling, and a walbro 485 outback. Those are my only high amperage pullers currently. I should also mention a small stereo setup using amps in the boot as well.

Is it more beneficial to locally ground these two items, well three, or should the pump and fan be part of the efi harness and grounded with all of the other accouterments? And wiring size for the grounds, I've always played the equal to the power size, but I am not an expert by any means. Thanks all!

Good question and also curious

It really depends on chassis construction and overall layout. That said for high 'dumb' loads I tend to string them outside of a harness when I can. Sometimes that means locally, sometimes that means going to a grounding block I've set up.

The chassis is a 300ZX unibody setup. Forgot to mention battery being relocated to rear. I plan on locally grounding the battery in the trunk area, and grounding chassis to engine via the oem grounding point up front. Trying to avoid loops and interference in the system.