My 1970 MGB loses power and misfires badly when I exceed 3000 rpm under load. In neutral, the engine will rev much higher.
I would check the point gap. You may need a cap, rotor, wires, plugs etc. A high voltage coil also might help if everything else is in good shape.
Unless the points, etc are nearly new, Just replace the whole set. Another possibility would be low compression. Run a compression check before you buy anything.
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