Tire size/brand suggestions for 1971 Chevrolet C/10 (130 MPH club)?

[AlBobRed]

Hello, this seemed the most appropriate forum to ask this type of question.  I am going to be driving down to Wendover from Minneapolis for World of Speed with the intention of attempting 130 MPH membership.  We have been playing around with tire/wheel combination's on this vehicle and like the feel and look or either 235/75-15 or 255/70-15 with the 255's being a bit more stable (on pavement that is).  Biggest problem with either of these sizes is that I have only found a very few speed rated models.

What would be some other options?  Any suggested sources for speed rated tires?

Any help would be fantastic.

Thanks,