[MACKL]

ChevLoRay,
You are correct. GM's first attempt at limiting the adjustment on the Idle air fuel adjusitng screws was to install plastic limiters that would pop off with a sharp wack on the end of a long screwdriver. Some time in the mid to late 70's, they switched to a hardened steel cap that were embeded in to the aluminum base plate. They also changed up the screw heads, the first was one you could turn with a screwdriver, the second was a screw head similar to the letter U, but top of the U looked just like the bottom. I think the actual term is a double D. (The lower part of our steering shafts have the same shape). The third was simply a 3/16" hex, except you woul have to grind the sides down on your socket before it would fit in the hole. You can buy a flexible cord tool that has both of the most common adjusters, one on each end. They shoud be sold at all of the major parts stores.

Syco67,
It is almost impossible to properly diagnose a carb via message board. The adjustments at the front base of the carb only adjust the IDLE air fuel mixture.
If you have fuel leaking out of the secondary throttle shafts, adjustment wont help. A carb works just like a toilet, except there is no handle to jiggle! Either you have a float level extremly too high, (splashing over the side), a float that is soaked with fuel causing it to be heavy, (allowing the needle and seat to seperate), or simply trash in between the needle and seat. All of which are easy to fix if you are carb savy. A nightmare if you are not.
If you have any questions, please let me know. Good luck...Kelly