To make things even more confusing the Ford parts catalog also uses the May 99 date as the cut off between the large SVT calipers and pads and the small SVT calipers and pads. Ford is not well know for accuracy in their parts catalogs. This may be correct but it is suspect. I think that BAT and SP Motorsports probably got their information from the Ford catalog.
I'm sure that the conversion was done before the 99 Cougar was introduced since it uses the same setup as the late SVT, but I don't think it was done on Job 1 of the 98 E1 SVT which was May of 98. (Oops, just discovered I had the wrong date here. The E1 started production 2/9/98)
Maybe we should start a survey of our SVT owners to see which brakes they have and what their build date is. The build date can be found on the warranty plate on the door.