I have a low gear set lockup Frankenstein 904 behind a Magnum stroker. It has stuff sourced from aftermarket, 32RE and A999 gearboxes. My buddy that helped me set it up said he'd call it a "34RE".

I've been pretty rough on it, though no passes yet, and haven't had any problems. It doesn't spin on the 2-3 upshift with the converter locked, that said, lockup is a bit scary if you're not expecting it. Not sure if I'd go that route for a car that is routinely drag raced as I'd fear for the input shaft. It is great for my purposes and when cruising, the lockup drops engine speed 300-500 RPM. A gear vendors in next in the project plan.

I control it with an adjustable pressure switch in the governor test port to close the circuit (lockup) at 52MPH and an adjustable vac switch to open the circuit (unlock) when you romp on it. I use a relay to unlock when I step on the brake. I've also got the governor tweaked to not upshift until a little over 5K at WOT (hence the need for the adjustable pressure switch).