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Sad as this is, I'd really like to see more pictures of the engine bay. Maybe the cradle isn't damaged.
Based upon what I've seen, I'd really be surprised if the cradle is damaged. I can't imagine anything flammable that would be situated anywhere near the cradle.
The typical Fiero "engine fire" scenario occurred when the (4 cylinder) rods flew out the front of the block, and all the vital fluids leaked out all over the catalytic converter. But this is a V6, that was running until it was parked.
Unless a fuel line ruptured, and sprayed gas all over something very hot (like the exhaust system) I'm thinking that the fire was up higher in the compartment. Maybe an electrical short, to the positive battery cable. Or leaves on the manifold, as was mentioned.
Just thinking out loud, really... Anybody's guess.