Dunno hey, my core is only 2 years old, coolant is Toyota Red and is 6 months old, Thermostat is genuine Toyota and is 6 months old.
I've got two 8 guages grounds (one on each head), and two 4 guage grounds (one on either side of the block), plus two 4 guage from the battery to the chassis (battery is in boot), so I doubt grounding is a problem on my motor.