Both have a 22" front spring section (center pin to center of front spring eye).
E-body rear section (center pin to center of rear spring eye) is 35", that era B is 36".
The shorter rear section will cause the rear shackles to either be vertical or point forward at the bottom.
Not a problem for rolling around the shop, but the springs will not work properly and the car should not be driven that way.
Using an extended front mount in the OP's scenario will move the center pin back, which moves the axle back (and the driveshaft @ ft yoke/trans).
Those front mounts are typically for using the 20" ft section SS springs in cars that have 21" or 22" section stock.