Help

[Ont67shortbox]

I jacked up the 67 and noticed a line worn on the drive shaft from the driveshaft loop.The bolt heads were also worn a bit from rubbing.The driveshaft is right in the center of the loop and not sure what is causing this,could it be a motor mount? I have stock ones,maybe I should go with the solid steel ones,I am at a loss any help would be great. Truck has a 427 w/auto, 3500 stall 486 gear and runs low 12s at 110 with a 1.7 60ft.