Clean the trigger points, too! Idle should be 1500 or so out of gear cold, and constant. Will drop rapidly as the engine warms up.
I'd also check for vac leaks and the condition of the idle air hoses and crankcase vent lines as leaks here will cause all sorts of trouble, especially on the Y-shaped idle air hose.
A bad vac lock line, leaking locks, leaking AC system, or brake booster line, or even an emission control line leaking will cause idle funnies.
So will the need for a complete tune-up. If you still have points in there, are they new? They get dirty on high milage cars from oil seepage, and will make trouble.
So will a sticky mechanical advance -- has it been oiled regularly (did you know it needed to be oiled? A drop or two of oil on the felt pad under the rotor every 5000 miles or less). If it sticks, it can snap back and forth rather than moving smoothly, causing idle speed variation.
A leaking vac retard on the distributor can make trouble, too.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!