It's my bet there have been more housings screwed up with spreaders than by tapping them in. All rear load rear axles have set preload. No spreaders used with them. I set the Danas with zero preload. Then add a .005" shim to each side. If you can't tap that setup in to the housing with a soft face dead blow you are doing something wrong. A large pry bar easily removes the carrier. If you are are concerned about hosing warpage you can do 3 things. #1 narrow it and use a setup bar before welding the ends on. #2 straighten it in a large press if it's tweeked. #3 what I've done is heat it cherry red on the side of the housing you want it to move towards and quench it. It will shrink and pull it towards the heated spot. You'll be amazed how far they will move when heated and then cooled. I've welded on a lot of housings. Never tweeked one bad enough I couldn't fix.
Doug