I've always thought a 3.09 gear 4 speed with something like a 2.94 axle ratio would make for a good setup. Pretty sure that works out to almost exactly what Passion's Hemi Overdrive would be like with a 3.55. But I assume you are referring to a 2.66 gear 4 speed, correct?
What about a TR-3550? Better strength and it bolts to the same QT bell as a T5.
Can't argue. If you are going to do it and do it right, T56 wins.
One thought I would add, the R154 hasn't been the best for Buschi on the drag strip. Worked fine on a road course, but didn't shift well enough to do well on the strip. At least that is what I remember him saying.