I was playing with the hot rod again today trying to figure out the coolant flow issues.
After driving the car for a while I parked it in the driveway and revved the snot out of it to heat soak the engine.
I shut the engine off and took measurements with my IR temp gun.

Old Auto Meter mechanical gauge: 235
Sending unit for mechanical gauge: 222
Top radiator tank on passenger side near hose: 239
Top radiator tank on driver side opposite hose: 233
Bottom passenger side tank opposite hose: 95
Bottom driver side tank near hose: 93
Driver side Edelbrock head measured on center of end: 195
Passenger side Edelbrock head measured close to center on end: 258

My alternator prevented me from measuring the same spot on each head but I got really close.

I've got to have something blocking the water to the passenger side of the engine.

What route does the coolant take through the engine?

It's obvious there's a flow obstruction since I've got a 140 degree temperature drop across the radiator.

The good news is that the monster cooling fan is certainly doing it's job.