Have you tried adjusting your vacuum modulator? Follow your vacuum line from your intake manifold to the modulator valve on the back of the transmission. Pull the hose off of the modulator valve and you will see an adjustment screw in there. If you turn that in, clockwise, it will raise the rpm at which your tranny shifts. If you back it out, counterclockwise, it will lower your shifting rpm. Assuming you want to raise your shifting point, you would want to turn it in, clockwise. If you have done all of this already, go to your parts store and see what other modulator valves they have. There are a couple different ones out there that should work. Also, if you pull the hose off of the modulator and there is tranny fluid in it, then it needs replaced, it is no good. Hope this helps.
If you have an adjustable modulator, they are designed to be adjusted for your performance engine, nothing wrong with having to adjust them.
Mine breaks the tires too. I have heard this is common when running shift kits, I have a stage-2 shift kit. I have the 285/70x15s with 3.50 gears in a 9 inch We're close on our setups, but I know you have me beat with the horsepower and torque
If you still aren't satisfied, you can go one step further and run a manual/automatic valve body and do your own shifting or let it shift automatic. I have this type of valve body as well.
I adjusted the screw clockwise, it took several turns. I didn't seat it, but it was beginning to stiffen. I'll take it out today and give it a try.
I don't know what the white stripe indicates, but it could be some aftermarket one such as TCI, I'm not really sure. Be careful not to seat the screw all the way in on the adjustment. Seems like I have read where if the transmission is run with it all the way seated it can cause problems. If it seats, I would back it out at least 1/2 to 1 turn. There is quite a bit of adjustability there with these modulators. I was noticing significant changes with just 1/2 turns. Keep us posted.