I need some more education about converters

I currently use a Ford converter in my 472 ci mod tractor. We weigh 5500# and are at about 500hp with 18.4 x 38 tires. We have a really competitive combination as it is, but I'm like everyone else and never satisfied. I seem to recall torque converters with stators having a variable pitch angle. Is there any product on the hi performance market like that? We are looking for a little bit more pull in the 2800 to 4500 rpm range, don't want stall speed increased and seem to be very well served with the cam Lem spec'd. Proably just wishful thinking, but ya don't know till ya ask!
Perry