I do not know of a good disk material for a diaphragm right now. I absolutely love mine in my Mustang, but it is a discontinued Kevlar dual material disk. I have not heard that there is a good alternative that can exceed the performance of a good Long style anymore. That being said, pedal pressure is awesomely comfortable, even without an assist spring under the dash
In the end though, I go Long on everything now due to simple performance and more choices. Great luck with Ram in more aggressive racers, although I run McLeod in my own vehicles, admittedly out of brand loyalty more than anything.
Additionally, the last CJ / TKO that hit the road with one of my engines had a Ram 3 finger and it did great, easy enough on the leg and we hit it pretty hard with drag radials and full Calvert suspension and it didn't even whimper
I would go with the correct Long style. Brent can likely set you up