The spring perches are about 1.5" further apart on each side. So they probably won't touch the springs, but I've used some chain to attach an axle to move a car before where the axle was too wide.

Another option is a F/M/J axle (Aspen, Diplomat, 5th Ave etc.) The spring pads will be in the right spot for a B body, just that the center pin holes are much larger.