It's just kinda dumb (IMO) to go through the hassle of changing a 904 for a 727 to go slower and get worse mileage. Likewise it's probably dumb to switch a 727 for a 904 if you already have the right parts in place. It's not worth the expense. I don't know if anyone else on this site has actually did the 727 to 904 swap and saw the actual difference on their timecards with no other changes?