For a 360 in a light pickup it doesn't matter. Any 8 3/4 center will do the trick.
I'd pick in this order:
1. Ratio
2. Sure Grip or not
3. Case casting number
If you're talking about a limited sip differential in a Chrysler Corp car, their trade name is Sure Grip.
Positraction is a General Motors trade name.
Mopar people get bent out of shape pretty easily if you use the GM term. Another example is "broadcast sheet" which in GM-speak is "build sheet"
It's kind of fun to learn and use the correct terms because it's like the club secret handshake.
R.