Try reversing the order of the spark plugs on the vey improbably chance that the last two (3&4) are defective and not firing.
Also the numbers on the spark plug boots indicate somebody has moved them around. Or something.
I get vertigo when I look at the picture but it looks to me like the distributor is 180* rotated. As best I recall #1 terminal on the distributor cap should be furthest from the engine.
TRUE GRIT
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