Can use some Thermostat and Rad Cap advice

Production engines have a safety bypass in the cooling system in case the stat jams shut. A portion of the returning coolant is bypassed to the feed side of the pump. The bypass is pretty big on the SB, so you might see some flow at idle when cold. If no stat, I would use a 180.

If you think the engine likes 12* initial timing with that cam, it will LOOOOOOOOOOOOOVE 20-25*. Move your dist with the engine running & see....