Yes, there is. The #2900 is a standard silicone seal, and the #2912 is the same seal made from a premium fluoroelastomer material. There's also a #BS-118291 offset double-lip seal for crank journals showing groove wear.
On the Summit site they show all those which I understand the difference in. They also show a 2909 seal which is the fluoroelastomer like the 2912 but it is $16 cheaper. The side by side comparison shows the 2912 fits v8,v6 and l6. The 2909 is for small block v8. Do you know if you can use the 2909?