as stated, no, this is not normal behavior no matter what thermostat you are running. something is wrong.

Also, the temp sending switch appears to have changed mid 1970s. non-leanburn part number is 4051140. So, I am sure this number is useless to you, even if it would work.

I found it under the electrical system if anyone wants to shoot him the previous number.

You might try blasting the heater while the car does this, just to make sure you didn't put the thermostat in backwards, or something. If the coolant really is getting hot like that, you'll feel it in the heater. under normal op, the temp should come up slowly. only in an overheat situation will it go full H. if you are missing coolant, it will overheat and sometimes not even move the gauge since it's now decoupled from what's going on in the block.

One last thing, I would never assume all went well with your reconditioning.