I thought belts stretched as much as 6-8" during a full speed head on crash. If so, you would need to replace them.
Mickey,
I would have to agree as I crushed the steering wheel on the left side due to the dash coming towards me and me going towards it. I think having an aluminum steering wheel was a big factor in minimizing chest damage. It bent alot where a steel one would not have.
Depending on the brand of belts, they could be sent back for a re-web. Save some money!!Throw the belts away and inspect everything in the seat monuting system as well .Toss all mounting bolts for the seat. If you moved that far, how far behind you were your belts mounted? If you keep the cage make sure it did not twist and crack some of the welds on top. Glad you were OK.