Originally Posted by RunswScissors
If you ever want to do discs, 9c1/Impala SS rear brakes fit the sedan axles without mods. You can get the discs to fit the wagon, but it's just another step you'll need to take. I don't really see an advantage of a wagon axle over the sedan, they are largely the same aside from the LCA mounting further outboard on the axle, and the frame is wider in the back. I guess it depends on what car you are putting it under, and if you can see an advantage of the different track width and slightly different suspension.
I have done 3 B-car frame swaps, the most recent about 3 weeks ago. I put a 94 9c1 frame under my 79 Coupe. Reading the comments above, I did it because the new frame was a southern frame from AZ, was already repainted, and had a completely rebuilt front and rear suspension. Much nicer than the crusty frame I had under the car. It's not a ton of work, we did the swap in 8 hours, and I'll never have to touch the frame again.
You can do it with a hoist, or with some forethought, some stands made out of 2x6's and a Cherry picker.. did that twice...
Regarding 8.5" sedan axles, I redrilled the axles on one of my bare 9c1 units. The backing plates from an earlier car will fit, but the hub locator flange on the 91-96 axles is larger, so my stock 9" drums would not fit. You can get a 91-96 with 9" drums, so I did that and drilled the pattern to 5x4.75". You can do this on a drill press. I transfer punched the pattern from my redrilled axle shafts (which were done on a mill with very good accuracy), and drilled the holes to 1/2" The drum located on the center flange, and gets clamped to the axle by the wheel, so getting the bolt pattern perfect is not very critical.
FWIW, you need to be careful with which axle you use from 91-96, there are 7.5" axles on a lot of those cars, 94-96 is a safer bet, but even then some 4.3L V8 cars were 7.5. There are also 2-3 different widths. Log on to impalassforum.com, there are stickes in the driveline section that detail the widths.
Regarding springs, it's a mixed bag. The junkyard is your friend. The rates are not often that different, but the free height is, so it changes your ride height among sedans. On wagons, they definitely had stiffer rear springs AND a taller free height.