On my 460, water temp in the front. Oil pressure in the rear, starter solenoid on a metal bracket close to my starter which is top mounted in the rear facing the front of the engine.
I mounted electrical boxes and such in the rear up high in the engine bay, secured with screws into composite foam that is secured via glue to the fiberglass.
I ran all my dash wires along the back and up the sides the of the boat tucked up under the ledge wrapped in black wire loom. One side of my boat had glassed in hook openings for the wire loom, the other did not. I glued in metal tabs and secured with zip ties to hold the loom and keep it tucked up.
If you want a clean look, just use wire loom and tuck as many cables as you can in a single run.
