If the intake manifold gasket in my 64 thunderbird with 80000 miles was just replaced and oil level is now at least 2 quarts above full mark could this cause engine to not crank over or seize?

Having the oil level at least two quarts above the full mark is extremely dangerous and could absolutely cause your engine to not crank or even seize. It's far more likely to prevent it from cranking than to cause it to seize immediately, though seizing is a very real possibility with continued operation at that oil level.

Here's why:

* Increased Crankcase Pressure: Excessive oil dramatically increases the pressure within the crankcase. This pressure can interfere with the operation of the oil pump, making it difficult or impossible for the engine to turn over. The starter motor may struggle against this excessive pressure.

* Oil Foaming: The increased volume and agitation of the oil can lead to foaming. Foamed oil loses its lubricating properties, leading to increased friction and potential damage to engine components.

* Oil Seal Damage: The excessive pressure can blow out oil seals, leading to oil leaks and further complications.

* Hydrostatic Lock: In extreme cases, excessive oil can enter the cylinders, preventing the pistons from moving freely. This is often referred to as "hydrostatic lock," and it will absolutely prevent the engine from turning over and can severely damage the engine.

* Connecting Rod Bearing Failure: The excess oil pressure and potential foaming can damage the bearings, leading to potentially catastrophic engine failure.

What to do IMMEDIATELY:

1. Do not attempt to crank the engine. This could cause irreversible damage.

2. Drain the excess oil. Carefully drain enough oil to bring the level back to the "full" mark on the dipstick. You'll need a drain pan and potentially a pump to remove the excess oil more quickly and safely.

3. Check for leaks: Inspect the area around the oil pan, valve covers, and the newly replaced intake manifold gasket for any signs of leaks. The excessive oil pressure might have forced oil past a seal.

4. Once the oil level is correct, attempt to crank the engine. If it still doesn't crank, you may have other issues, but at least you've addressed the immediate danger.

5. Have the engine checked by a mechanic. It's crucial to have a professional inspect the engine for any damage caused by the overfilling.

The fact that the intake manifold gasket was recently replaced is largely irrelevant to this specific problem, though you should definitely ensure the new gasket is correctly installed. The problem is solely the massively overfilled oil level. Get that corrected immediately.