Mark,

I've had several throttle body/ butterfly shaft aluminum castings
rebushed for carbs I'm rebuilding.  The normal route is to ask at the
parts houses that have a machine shop for the local resouce to do it.

The procedure is to machine out the hole, rebush, and your done. Costs
around $40. The bushings are available as a rebuild for Rochester Carbs
and are manufactured by Delco.

The other route could/ would be to go to a starter rebuild shop.  They
typically do this same procedure to replace the nose cone bushing on starters.

I hope this helps.

Sincerely,

Mark Keller
91 Carat
Cowichan Bay BC