One thing I've never seen done real nice is a fire wall that follows the shape of the engine and still allows service. If you got a 4" thick piece of foam, Installed the drivetrain, then shaped the foam to tuck around the back of the motor and trans with an inch clearance, then pull the valve covers, Dist. etc. to make sure service was good. Replicate the final shape in metal and it would be beautiful! Just a wild thought, but you have the skills to pull it off.