I actually bought this rear from SD, I compared it to my other rear and it doesn't look like the shock mounts have been moved. They are right up against the 9 inch ends. Here are some pics.
Judging by the looks of it, my housing that is narrowed likes about 1" before getting against the shock brackets. So 2" would be right on them. I went 1" on each side.
Im going to take mine out shortly. Got all the parts now expect my new gears, thanks guys. Anyone still rock a 15x10 with 7.5BS? I just want mine tucked hard. I hope it all works out lol