A diff drop wont have anything to do with this contact.
ALL Aftermarket skids are very tight through there, space it down with a metal washer or two and you'll be fine. If you are still worried clamp it in a vice and tweak it a couple degrees. This isn't a big deal, all of our trucks are at least 13 years old and none of them are exactly the same. Aftermarket parts sometimes require a little extra effort to be perfect.
I know my Savage skids have made contact there after being used for what they are designed for, sliding over rocks.