Cobra Caliper Questions - Urgent!

I recently bought from eBay, a pair of "Used 96-98 Cobra front brake calipers" with brackets. I know what you're thinking, all 94-98 are the same. I don't know what the seller was thinking, but read on. They needed rebuilt (boots were melted) so I ordered the seal kits. While I was waiting for the kits to arrive, I noticed something extremely weird. These calipers have a date code of 98, but they have the larger (40.5mm vs. 38mm) pistons. Even weirder, they have coarse threads for the banjo bolts, like the 03-04 calipers. So...WTF IS THIS? lol...

On a related note, the only rebuild kits available are for the 38mm piston calipers. I called the local Mustang store (CJ Pony Parts) and they said the kit would still work, so I installed it, and can verify that it fits. I DID have to stretch the seals a bit, put them in quick, and install the piston before the seal went completely back to its normal size.

So my two questions are:
Why are these calipers so weird?
-and-
Is it ok to use the 38mm caliper seals on the 40.5mm piston?
 
I wouldnt know myself but absent folks over here knowing, you might want to post on the 94-95 side. Those guys are always doing brake swaps and are very conversant with the ins-and-outs of the brakes through the SN years.

Good luck.
 
There were Piston Diameter changes and Thread Pitch changes throughout the years, so it sounds normal, I would make sure I used the correct Pistons and Seals for the Caliper.