This is one I've never seen before
http://www.ebay.com/itm/Model-T-Ford-Accessory-Manifold-Vaporator-MT-1234-/40137 8613749?hash=item5d740799f5:g:9VwAAOSwBcpZhMpO
I'd almost bet that it would never warp. If it did, it would be easy to true back up due to on piece design.