According to
Fast Larry's Bandit FAQ the Radio Shack "Shim Set" Part is # 64-3022A. Since this was published (several years ago) there have been some reports that the washers in this kit that are the ID to fit the needles have a larger OD than original, others say they have no problems, so it may be they get the washers from different suppliers. If the OD is too large, it will hang up inside the slide and hold the needle much higher, so my advice is whatever source you use for the washers/shims be sure they'll go all the way to the bottom of the slide without hanging up. If they do hang up, you can make them smaller with a sanding disc.
Don't know that there's a "good post" on shimming - it's pretty simple to do. Remove the carb tops (and take care not to loose the little O rings), pull out the diaphragm and slide assy, pull the needles out of the slides (needle nose pliers are very handy for this) and put a shim under the E clip on the needles - between the E clip and the spacers that are already there. Reassemble.
That said, I think you'll be even happier with a jet kit though. I was reluctant to rejet myself, but took the dive and am glad I did.