1934 Pickup overheating issues

[Kevin Marsh]

Hello all, I could use your help. I wrapped up the restoration on a 34 pickup a little over a year ago. The owner participated in a couple parades last summer, and each time the engine overheated and coolant boiled over.
The engine is a fresh rebuild by a very experienced flathead specialist, the radiator also received a new modern style core, new water pumps with the improved impellor design and the stock four blade fan. Total miles driven so far are 45, and on the open road the engine runs between 170 and 180 degrees.
I realize the engine will run cooler with more miles driven and a sufficient break in period, but for now I need to do something to aid during the extreme conditions during parades as I know he will be doing more of those this summer.
I have tried to research the thermostats made by Bob Shewman that fit into the upper hoses, that have been discussed in several forums. The majority of the posts relate to bringing the engine temperature up, because the vehicle run too cool and never quite get to operating temperature. I am wondering about their effectiveness in maintaining the temperature during slow driving conditions such as a parade.
Ideally, the thermostat should allow sufficient time for the water in the radiator to cool before it cycles back into the motor. From what I have read about the Shewman thermostats they have bypass holes to prevent a surge of pressure when they reach temperature and open. Will that limit the amount of cooling efficiency of the radiator?
I would appreciate any feedback from those who my have encountered a similar situation, or have experience with these thermostats. I found an email contact for Bob Shewman ([email protected]) and have sent him an inquiry as well with no response back, so I am wondering if that is no longer a valid contact. If anyone has his current information I would appreciate that as well.
Thank you for your assistance.