"When its at
operational temps the idle rpms rise and lower slowly and then
eventually the
engine cuts off, especially at lights. Any ideas?"

Check that the pre-heat tube isn't clogged, as this can cause carb
icing. You can test it by BRIEFLY touching the preheat tube once the
engine is warmed up. It should be hot enough to burn you on both sides,
if not you need to focus on repairing that problem first. Fixing it is
rather straightforward, remove the intake manifold and then use an old
clutch cable to clear it out. Chuck the threaded end of the cable into
a drill and cut the cable so it is slightly longer than half the length
of the intake. Use it as a roto-rooter type tool with the drill to
clear out the carbon. Work it from both sides and use compressed air as
needed to remove the chunks as you progress. If this is the problem
you'll be amazed at how much better your bug runs when you are done
with this job.

The other possibility is that the carburetor itself is in need of an
overhaul, or you may have an air leak around the throttle shaft. The
latter is fairly easy to test, get the car warmed up and while idling
spray some carb cleaner around the ends of the throttle shaft. If the
idle goes up you have an air leak. Fixing it requires the bushings in
the carb body to be replaced.

http://www.rimcovw.com/misc.htm

Looks like 40 bucks will get you a properly repaired carb casting that
you can overhaul and put back in service. Alternatively you could
purchase a new carburetor. If you don't find evidence of an air leak
around the throttle shaft you could just overhaul your existing carb.
The overhaul kit usually runs about 10 bucks.

Chris