I decided on the Tundra Lite Tailwheel http://www.tundratailwheel.com/
I bought the 8" tall model and was told it will mate to the T3 tailwheel spring, which is also on order.
The Tundra Lite can be locked so the airplane will run straight on the ground. It can be easily unlocked for taxiing.
My Dad flew P-51's in WWII and also had tons of time in an AT-6. I remember him telling me that the P-51 had a locking tailwheel and I think some of the AT-6's did also.
He said when your putting a 200 hour student in a P-51 - the locking tailwheel really helped them make the transition from the AT-6 to the 51.
I have, in reality zero tailwheel time, but I am in the process of converting from nosegear to taildragger so I can go play with some friends on the sandbars on the Red River, between Texas and Oklahoma. It's like thirteen miles south of my house.
So, I am hoping that the investment in a locking tailwheel will help in transition training I'm looking forward too. That plus a lot of practice running up and down the runway. Can't wait to get started.
Regards
Rodney