Hey...If they can both be built to withstand the torque for about the same cost, I'd look at the 200-4R as well. The 2.74 to 1.57 1st to 2nd is a less radical rpm drop and it has a .67 OD, the best of any automatic OD that fits these cars. The 200-4R is based on the 200 series which was sorta similar to the TH350 series. I know many Drag Race guys were using Art Carr built 200-4Rs in the Grand National Buicks...a car was not exactly a feather weight.
For me, my tires go up in smoke beyond 1/2 throttle anyway. Whatever transmission I have would not see the full abuse unless I had stickier tires.