I seem to remember that there first responder communication recordings that referenced other explosives. There was also an article by a British military expert that claimed that the bomb alleged to be used wouldn’t operate the way the FBI claimed it did.
I am no structural engineer, but I stood right at the edge of the huge crater that was created by the blast. It was massive and very deep. I have no issues believing that it caused the damage that occurred. I was for a time, on the south side (plaza) side of the building...and it was largely undamaged. Windows blown out, but the offices on that side still have pictures and plaques hanging on the walls. So I believe that truck bomb was responsible.