The choke is the top butterfly plate in the front. The choke pull off uses ported vacuum, like the vacuum advance, to open the choke when the engine is off-idle. If you do not have a vacuum gauge, find a manifold vacuum port and hook it to the pull-off, it should open the choke. You may need to open the throttle plate a RCH just so the pull-off doesn't bind up (it's made to pull off when you hit the throttle). Your PCV and brake booster are manifold vacuum. You may need a DD socket to adjust the mixture screws, depends on the years. Most of the pro tool companies have a carb adjusting tool.
http://buy1.snapon.com/catalog/item....re&dir=catalog Well worth the money in my opinion, keeps your fingers out of belts, fans and pulleys. As stated earlier, check the electric choke as well. Basically if it runs bad at idle it is probably not the pull-off, if it runs bad off-idle check the pull-off. That carb looks like it is in decent shape. What ever you do not trade it in for a rebuilt carb. If you buy a rebuilt carb keep that one, do not take it in as a core. The Q-Jets that you get from autopart stores are usually beat and have been rebuilt too many times.