Ted,
NAPA and other auto parts stores should have studs that will work. You should be able to measure what you need (length of threaded bottom and threaded top plus the thickness of the spacer/insulator. (as posted above by Ted) Add a little for a lock washer - to not get them too long because on some carbs you do not have much space above the post (to allow the placement of the nut).
A vise grip or a
stud extractor should remove the old bolt - be careful they break. Soak with a penetrating oil and heat and cool the bolt bottom a few times.
