I'm saying that the difference betwenn a 2500# and a 3300# car is not enough to make it possible to get away with running more through the transmission.
The internal gear journals of the mainshafts are the same on any mainshaft in a toploader. The difference is behind the rear bearing all the way to the splines and in front of the input bearing all the way to the splines.
28 spline on top, 31 spline on bottom
1 1/16" input on the left, 1 3/8" input on the right.