Editorial Comment:
You are participating in a classic American motor sport which can be a lot of fun to watch as well as participate in.

The first thing that comes to my mind in your situation is the high pressure which you're using for the tires. Of course, this might depend on the tire itself, but it seems to be close to or maybe even over what is recommended for most tires of that size. Check what is stamped on the side wall for maximum pressure, and if this is less than what you're using, this may be the key to solving your problem.

Also, because of the weight you may want to see what kind of load rating your current tires have and compare this to the actual weight which each tire carries. The load rating, is for each tire, so if it is 950 lbs. and your front end, fully loaded is less than 1900 lbs. you should be OK, but if you are close to that, or exceeding it you might want to look at finding tires with a higher load rating.

The speed rating of your tires might also be a consideration, but generally speaking, tires which are designed for heavier loads are not usually made for higher speeds.

You may have to consider changing your wheel size in order to get tires which are more durable under the circumstances which you are using them.

Those are a few of the thoughts which come to mind, I know they don't solve your problem, but perhaps they may help you in seeking a solution.

TG