560" Alum "B" block, B-1 alum heads, 8-71, 570° @ idle, about 1050-1075 at 7000, drag app in a 2100# altered . . EGT @ 1 & 8 . .
My guess is somewhere between 1000 & 1125° . . any more than that and you're treading in dangerous water . . If you're above that, start looking at your plugs closely . . But that's just an opinion . .