That's weird, never had that problem with any of my 2nd gen F-bodies... I would either a) cut the interior tub BEHIND the rear line of the doors and use strip styrene to extend it the 1/4" or whatever... OR I would use really thin sheet styrene and glue it to the front of the dash, then putty it and sand it smooth to give it the appearance of just having a bigger dash... which isn't really accurate mind you.