I am not to sure if it would be a good idea to block off the water-pump bye-pass tube on vehicles that have them. I know the Early Ford V8's did not have a bye-pass, the Y-Blocks did, don't recall seeing a bye-pass tube on an 8BA-8CM engine.
I know from first hand experience with the 59AB engine in my '36, if the thermostat sticks in the closed position on a hot day, you have a big problem.
In 1954 I was driving my '36 back to Vegas from So Cal. I was pulling the Baker Grade which is just northerly of Baker, CA., almost sea level climbing to over 4,k ft. About half way up the hill my Ford got really hot. That section of road is very desolate, I knew the road, knowing that the grade would flatten out about half way up and there was a service station there.
By the time I pulled into the station the car was a tea kettle, spraying water on the radiator cooled things down a little so we let the car sit for awhile. After the engine cooled down I started the engine and started to put water in the radiator, the engine temp stated to rise, not a good sign, walked around the car, steam was coming out of the right side exhaust, another bad sign.
A little investigative work revealed that the right head gasket was blown.
We pulled the head, the stat was stuck in the closed position. We checked the 'Offy' head, it was warped. Since this was 1954 I walked into the service station, purchased two new head gaskets and a can of Permatex sealant.
We put two head gaskets and a lot of sealant on the right head, reinstalled the head, filled the radiator with water and drove the 90 miles to Vegas. The next day I pulled both heads, had them surfaced to make them flat, installed the heads with new stats and drove the car until the engine broke a piston in the fall of '58.