Recently discovered water in the fuel also shares these symptoms. Rich, rich, lean, rich, lean, lean ....dead.
Drained 5 liter into a clear bottle came back and saw a 3rd being water. Paid the station a visit and it turned out that other people have been suffering too for a week or two.

Another cause of 'won't rev over 4000 RPM' is too far advanced timing. But that won't cause the problem of choking(running rich).

Most likely: fuel problems

You can solve this without changing lots of parts in the hope of stumbling across the solution.

* Drain and refill the tank
* Change the fuel filter
* Drain and rinse the carby fuel bowl

If that doesn't clear up the problem there are other potential cause (perhaps electrical). But start with the most common -- it's relatively easy to do this.

Crap in fuel tank, blocked fuel filter.
If its only just started happening it wont be low float level or wrong jets.
Might still be electrical..

Constant trouble with car: starting (dead), back firing, chokes once warmed up so changed: coil, balister resister, spark plugs, points, dizzy, condenser. Thinking about putting in an electronic ignition though other locals still use points so not sure what the car's issue is?

Could it be vacuum in the carby?