I think you can send them (your MIB files) to Solarwinds support and make your request to integrate them into the Orion MIB database then later you can get that new Orion file and update your system. I've heard it is a quick turn around. I've never had to do this myself but I've read of this an offer from the support folks.
Have you seen this UnDP with a good explaination on how to use it:
It's called Cisco 6500 Fabric Utliziation:
These UnDPs poll values from the Cisco-CAT6K-CROSSBAR-MIB. They will return inbound and outbound percent utilization for the switch fabric.
Also lchance is correct... here's what I would do though I think the mib you want is already in SolarWinds as you see in my previous post people have been doing this for while already with 6500 switchfabric/backplane:
To Open a Ticket: www.solarwinds.com/.../ticket
Oh yeah quick correction... For getting data with the UnDP, the MIB doesn't actually have to be in the Orion MIB database. You only need to provide the OID in the proper field and Orion will be able to get the data.