Tom;

It sounds to me as though you are describing two different (and really typical) symptoms, and trying to relate them into one cause. I'll seperate them...

Cooling: When stopped, and idling, temperature will always tend to creep upward due to the reduced circulation at lower RPMs...this may be exacerbated by a low cooling system level, poor circulation, funky t-stat, but seeing the cylcing on the temp needle noticably is not terribly unusual (as long as it does this in a reasonable operating range, and does not go totally into the red). Check and top up your coolant level...upgrade to a sealed system to stop cooling system incontenance, and you may want to check calibration of your gauge to make sure you can trust what its showing you also. See: http://www.intelab.com/swem/service%20notes.htm#Cooling%20System

Bogging at prolonged idle: Even presuming a decent state of ignition and carb tuning, this is also not really unusual...if the mixture and synchronization at idle is not set perfectly (and what 40 year old SU carbs, maybe sucking a little false air are?), the spark-plugs will start to "load up" at prolonged idle... blipping the throttle, clears it for a while until plugs load up again...try leaning mixture just a bit (especially for the summer), in the winter you get better throttle response when slightly richer...I change my mixture by a half turn from cold to warm seasons. Also make certain you choke is returning fully...try also to raise your fast idle while choked...that will prevent plug loading while choked and warming.

Good Hunting