Thanks for the help.
I purchased the extensions from eBay. They do not fit. They are too long, and the threaded portion is smaller than the holes in my "box".
I also tried to look up the parts on circle kf. I was confused because the parts listing for these holes shows that 1/2 in pipe thread plugs were used, but it lists that 4 are required. My "box" only has 2 holes to allow for carburator adjustment.
If the holes can be plugged with 1/2 inch pipe plugs I can easily plug them. I wondered if the factory plugs were probably slotted for screw driver insertion and removal?
All help in this matter is GREATLY APPRECIATED!