FACTORY SIZE TIRES

I just had this conversation with my brother tonight. He is building a 69 Firebird 350 HO 3sp car for stock class ... I was wondering why nobody runs a 440 Dart or Barracuda in the FAST class .?
If you are
talking about tha a-body 440s, its cause they have to run stock exhaust manifolds, and a-body 440 manifolds are about five grand.