chris
no problem rambling
ask away
as this shows
Up to 50 amps: 8 AWG
Up to 65 amps: 6 AWG
Up to 85 amps: 4 AWG
but it will be a rare moment that you will need to charge any battery at full drain, (really about 10 volts to full charge of 13.4) so the eight gauge should be fine. your distance is alternator to block to starter, about 6-7'
question: does any modern truck that has a 12si have a 4 ga wire off the alt lug? to the battery??
no
buy wire in bulk not by the foot. as you said maybe a total of 300'. i'm more inclined @ 200'
very surprising thought and not many think about just what goes into a wire kit. 18-8 gauge, mostly 14 and 16 ga. in 4-5+ colors. i have 6 wires (tail,brake,left,right,back-up,ground) almost the length of the truck to the rear. add 4-5 going across the rear. i have two clearance/ running lights on the running boards just below the doors, (one as a running and the other is a side blinker) that's 100'+. under bed fuel tank.
behind the dash, cigarette lighter,gauges, door switches, courtesy lamps, glove box lamp, indicator dash lamps maybe 100'
engine compartment, DA plug, wiper motor, window squirter, electric choke, temp, hei, tach, fan, headlights and blinkers, all those relays, each relay has four different wires and one must go into the cab to a switch. a heavier wire to power block ( about 1-2' depending on where you place the relay panel. i have a panel i made w/ room for 8 relays, i'm using 6. the power block is about 1' away. everything needs very good grounding, those are fairly short. i run a separate gnd to the rear (one of those 5-6), cab to frame to bed to radiator frame to engine.
& split black housing to cover it all, in various sizes 1/4 - 5/8'', black tape, 4-5 dozen solderless connectors various sizes, heat shrink various sizes.
lots of fun work.
gosh did i mention speaker wire??
they can order the 12 ga fuse wire
you have electric doors windows air compressor &&& ??
grounds are green, hot voltage is red, lights are blue, make up the rest
you may be right 300'
