This article by Bob Bidonde argues that, as Railcarmover mentions above, the indented firewall change combined the relocation of the fuel cutoff with the relocation of the steering column support bracket to eliminate both of the potential ways for gasoline to leak into the cabin.
Per the article, "several cities would not license Model A Taxis because of the potential for gasoline leakage inside the car." So perhaps that's the truth behind the "state laws" claim.
http://www.ahooga.com/notebook/howto...t_firewall.pdf