Bill:
The bypass type valve showed up on later vehicles where the thermostat has two valve seats. On those setups, the heater is the bypass circuit, and needs to keep flowing in the summer months.
For the mopars with the big bypass hose you can just shut the water off to the heater core.
I guess the OP is driving a 100 point show car. I posted the part number for a mopar OEM manual coolant shutoff valve that was a regional dealer install item in the 60's & 70's. I would rather install that valve once & leave my coolant system closed up than pull a hose twice a year to jam a foreign object in the line.
B.
