FIRST, check the rear track width of the B-body item you perceive you want to use. Not many B-body rear axles have the width to be under a C-body, unless it might be the '68 and prior C-body models.
Seems like the '71+ B-body wagons had a approx 63" rear track, but station wagons ONLY? Which allowed the wheel tubs to be wide enough to allow a 4x8" plywood panel to be put in the cargo/load floor area.
Spring saddle width will be different, too, even if the track width is similar.
What's the issue with your current C-body rear axle? Just curious.
CBODY67