Can anyone tell me what diameter hole to drill to install tang bushings for the superposed trigger guard tang screws. Thanks,

I would measure the bushing and select the appropriate drill. Don't know any other way.

Well the bushing has little 'teeth' that are greater diameter than the bushing body to keep the bushing from pulling out when tightening the screw. I would have to go measure but I believe about .015-.020"greater from memory. Do you think that a hole the diameter of the body would suffice.

The bushing is indeed about .020 larger than the hole. It's driven in about 1/64th below the bottom of the wood and then a drop of superglue is allowed to soak into the joint between the wood and bushing. Don't get it in the threads or you will have to chase the threads with a tap. I put some modeling clay in the threaded hole while gluing.

Thanks so much. This is what I was after.