That aluminum lower piece of the clutch is actually a nut. the actually briggs tool looks something like a spanner wrench. In a pinch you can put something soft against those little ears, which are just places for screws to hold the screen on. and tap on it to loosen the nut. Some of the clutch bases had places for four screws but only used two, so if that is the case you may be able to get a little rougher with the unused tabs.
It sounds like you have the points and condenser under the flywheel type so it will have to come off. And from your code number your engine is a 1981. and next time just point in one location. Multiple post confuse everybody, and you end up with responses in various locations and is hard to keep track off.