Lug Studs and Nuts

Any idea where one can get 3 LH and 3 RH lug studs and lug nuts for 1949 IHC KB3?

Do not fall into that stupid keep it all original trap. This is a good time to replace all of the studs with right hand thread studs and new nuts. Those studs and nuts, in right hand are common. NAPA should have them.
If you have a few broken studs, it is very likely that they broke from stress, load cycling and old age. It is reasonable to assume the other studs are about to fail.
A full set of new studs and nuts will buy a lot of safety and will likely cost less than $40.
If after knowing what you now know and do not replace , a failure could cost you everything you own and hope to own, in a claim. Your insurance will not cover you in this. The fine print requires you to maintain your vehicle to a standard. If you do not do so, the insurance company will drop you like a fresh turd.

That’s great… do you know the Napa part number?