I had a 256 open my my 68 400 with AC. (Only a 256 was available on AC 400 cars.) To keep mine looking stock, I used the original housing and installed Eaton 355 posi internals. So, still have the "XB" housing with much better performance. My local rear end guy charged me about $1,200 for the parts and set-up. Prior to rebuild, I sand-blasted and epoxy primed the rear-end. After the rebuild I painted it. It looks great and performs better.