OK, the phone is ringing off the hook, the mail box is full, and we're having to go thru the core pile to locate throttle bodies for folks.
It appears that someone figured out that you can buy a "stepped" drill bit for about $7 from Grainger and bore each side of your throttle body out to install a couple of dollars worth of bushings from the same source.
Since a stepped drill bit is NOT self guiding, and only cuts on one side....well, you can figure out why it isn't such a a good idea.
Another well meaning hobbyist found some thin brass tubing at the hardware store and the next size drillbit and bored into both sides and pushed in a cut piece of the brass tubing. I've had a few of these sent here and thankfully our bushing installation kits self guiding 3/8" bit took all of that right out and successfully but a self lubricating bronze bushing in place.
Now here's the real kicker. Recently a TV show shows how to rebuild a Quadrajet, and they showed just taking a plain old 3/8" drill bit and boring into the throttle body to install bronze bushings. Well, since a drill but only cuts on two sides at once, and isn't self guiding......NOT a good idea.
In any case, if this trend continues we will run out of spare throttle bodies quickly.
The only successful method for the "do it yourselfer" is to use a custom ground self guiding bit. It will but a perfect hole on center every single time.
They are available directly off the website, and each bit is hand sharpened and tested in our shop before shipping......Cliff