Putting aside the chamber placement relative to the bore. Look at where the plugs are on all these heads relative to the exhaust/intake valve. Notice on the M6049SC1 and M6049E1 the plug tip will not likely get as exposed to the ex valve flow path and chambers combustion heat path. They are more biased to the center closer to the "cooler" intake side. First glance they look similar but they arent.
My bigger concern would be exposing the ground strap to more heat than needed.
pages start around 112 in the pdf file
http://www.fordracingparts.com/2011-...0Catalog_A.pdf