They just might be-an axle with the VIN was found in WTC part I which led to a name and storage facility rented in the perps name, IIRC..
Parts -- rear axles in both cases, I think -- were found in the WTC and OKC bombings. In WTC, the dumbass went back to the rental office, claimed the truck was stolen, and asked for his deposit back. In WTC, I think they'd used fake documents, so it was a little tougher to track them down.