Jim how much HP/Torque will one of your modded SP torque converters handle? I have a 650 HP Stg 2 Buick producing 630 ft/lbs of torque.
For street/light strip use with street radials, in a car less than 4000 lbs, with a gear ratio of 3,42 or higher, I would not worry about durability. Sustained drag/street racing with slicks or sticky dot's, trans brakes, and heavy, powerful cars, with numerically low rear end gears would be the cars/applications I would worry about, and think the appropriate small diameter Fixed pitch converter (Like my 9.5") are a much better fit for this. I have never had a 12/13" VP converter fail in an A body. JW
I have one of Jim's 12" VP converters in my GS. I use 275/60 MT Drag Radials. I have approximately 20 passes on it in the mid to high 11's. Best 60' has been 1.62. The car weighs 4020 lbs with me in it, nothing in the trunk, and 1/2 a tank of gas.
I know a guy with a switch pitch he moves between two of his Chevy's, running ~700HP (BBC with a 6-71 blower), and ran high-10's in a ~3,300lb car, and high-9's in a ~2,800lb car, and put over 100,000 miles on the transmission before freshing it up (built the first car in the 90's). I don't believe he did anything with the converter at that time. It's high-stall is around 3,500rpm iirc, might be 3,000rpm. He doesn't seem overly concerned about its durability!
Jim, I have one of your 12 inch converters that I bought from Ed W when he went back to stock. is the core value on this worth more to you than a stock converter? I've not touched it since I bought it.