The plugs usually blend in and are hard to see. They are at the front bottom of the carb., basically against the gasket. One on the left, one on the right, something like 3" or 4" apart. I have never had to pull the plugs out of one, but I think you use a self tapping screw and pull them out with channel locks or something similar by pulling on the screw. A slide hammer would be ideal. A 454 quadrajet could work, but it will need a lot of tuning. I suspect you would have to change the jets and metering rods in addition to normal adjustments.