I'd leave the dizzy. you could open a whole can of worms there and spend a lot of time finding the worms and putting them back.
1980 series 3. I think it could be a small hole in the diaphram of the emission control system. This bit of apparatus is not covered by the Haynes manual.
The diaphram lives in a little house near the carb. It is connected to the carb by a bit of rubber hose and the valve rocker cover by another bit of rubber hose. What often happens is, a hole appears in the rubber diaphram. Air leaks in, dilutes fuel/air mix and when you try to accelerate this air weakens the mixture, at the precise moment it needs to be richened.
It is about 3 inches diameter with some wire clips on the top. Undo clips, take top off and lift out rubber. See if it has a hole in it - you need to be invery good daylight for this.
The symptoms are very similar to ignition problems,distributer, plugs, fuel filter etc.
Do check the emision control. Its a crap system. I stripped it off and put a plug in the hole left in inlet manifold. First time I'd bought a part for motor vehicle from a plumbers merchants!
This is all a bit tricky to describe without a diagram.
I've been to hell and back for 12 months - new dizzy, points, condenser etc. New carb ages ago. Turned out to be this rubber diaphram.
I agree with in line fuel filter. They cost nothing and are easy to fit.