Do the newer magnum style thermostats flow enough

with no stat, the coolant will circulate to quickly and not pull the heat out, running even hotter. Thats why drag cars run restrictor washers in place of ta stat. slow it down so it can remove heat in both engine and rad. '
OP call b cool or whoever you got it from and ask HP rating of rad. If they say more than 375 then they are full of crap. We have a 22" 2 row aluminum, nothing fancy, just well made under $185 and ita rated at 375. I would say mild 360 would be fine but nothing more. The 3 row version is rated at 500 which is probably where you need to be as 416 should be 400-450 pretty easy. You need a shroud too, or go elecctric.