What ever gauge you end up with, try to make it as wide/thick as you can get away with as this will aid in the flow of amperage. As for length of cable, I just happen to have an old cable pulled from a GTV6 which should be the same length for the Alfetta. I measured 188" inches after 3 tries to straighten out the cable and getting slightly different measurements. 188" is the longest measurement. Best bet might be to go 100" + and then cut/clip exess either in the engine bay or back at the trunk/battery.
67 Duetto - Angelina
73 GTV - race car restoration
84 GTV6 - Signore Busso - GyroDisc Brakes, RSR Suspension, Jemison T/A, CSC SS exhaust
95 164LS - Black Bomber - 6sp w/Q2 LSD, Highway Cruise Rocket
Previous Alfas: 76, 78, 2ea 79 Alfetta GT, 78 Alfetta Sports Sedan, 86 & 87 Milano Verde, 86 Gold Milano (Mirko's race car), 94 164 LS 5sp (parted), 94 164 LS Auto (5sp conversion) - traded for '84 Interceptor.
84 VF1000F Honda Interceptor
07 VFR800 Interceptor, 25th Ann Edition
"Never apologize, never explain; your true friends don't need it, and your true enemies will not believe you anyway."