Ultimate 8" from Lenny. With a 5.14 rear gear and a 104 rollout tire, it would flash to 7200 rpm, yet was very driveable.
Great converters! I run an Ultimate/Lenny 8 1/2" 5500 behind a 540, with 4.10s. Totally street driven. Never had any heating issues with a good cooler and deep pan.