I have had dozens and dozens of Coker tires and have had nothing but good luck with them. All were bias ply. I have no experience with radials...
Kontio has been around for a few years now, and they can be found from some normal online suppliers and possibly local suppliers.
I put a set of "Coker Classics" on my '51 about 12 years ago. I had no problems; two took no weights to balance, another an ounce or so, and the last one was 2 ounces. They still look good, but am considering replacing them for age reasons alone. This time. I'm going to try Contio, because of good reports and PRICE (less than half the cost now of Cokers back then).