I'm supposed to take a break from cad during lunch, but a picture explains it so much more.

Ignore the ford 9" center part, that's just what I have on my work computer.
Since you are sticking with your current brakes, the axle flange to caliper mounting bracket flange dimension will not change. Since the axle flange to axle flange measurement won't change, where the caliper bracket bolts to the housing flange will stay the same.
Whatever the new housing end measures for width, subtract that much from the existing caliper mount flange and then weld new ends on. The bearings will ride further back on the new axles. I would talk to whomever you plan to order axles from to make sure the brake standoff is something they can build. I'm almost positive they will, but it would make for a bad suprise after the housing is modified if they can't.
Old bearing setup on top, new on bottom.