Strange problem help please

[Ont67shortbox]

I was out on the weekend with the truck,ran pretty good for the first time out. I got home and was checking things out and where the drive shaft passes through the cross member there is a line like it was rubbing all around.the shaft is centered in the crossmember hole and I have no idea what would cause this?I know the truck is not caged but could it be twisting on launch and causing this? its a 427 bbc with around 450 hp,runs low 12s not like its a torque monster or aything but this is something new its doing.I have stock motor mounts with the good trans mount,baffled thanks for any help Brian