This has actually been done by a friend of mine. He simply took a Chevelle convertible and transfered all the body parts from a Monte Carlo onto it including the firewall. A cowl induction hood was fabricated using an original Chevelle hood and grafted that onto the Monte hood. It was actually quite a simple transformation (all things considered) and turned out beautifully. This car was sold at BJ about 5 years ago, red with an LS-6. So there goes the "no Monte convert and/or LS-6 Monte" theory.
