You can NOT underdrive the pump that far. You have a kick *** radiator. As RRR said, you NEED a Flowkooler pump and some overdriven pulleys. And a Stewart Components thermostat. There is nothing like it on the market. These are the old Robert Shaw thermostats.
You’ve got most of what you need with the radiator. Now you need a couple of little thangs and you’ll be pooping in the tall cotton.
EDIT: I forgot to mention you need to throw the shroud away and use a spacer to get the fan about an inch away from the radiator. If you get it that close, you want need a shroud. It will be close enough to the radiator to pull plenty of air at idle (if you get the pump speed, and by mechanical connecting the fan speed up where it should be) to keep it cool at at high speeds the shroud won’t be packing air.
