I just did the swap, and only swapped the bladder. The weight sensors were not swapped. My stock convertible seats were not used for the swapped. I ended up buying a 2011 GT seat and used that bladder on the 2014 Mustang GT Recaro's. No issues or check engine lights.
I purchased a set off Ebay. Had no issued with them. However, ended up upgrading to Eradispeed two piece rotors which came with adapters. I just sold the rear adapters I bought from Ebay. I tried to find them on Ebay, but couldn't fine the ad.