Their is another light switch , which is the one you have, that is not referenced in the light switch post earlier in this thread. It looks like the one on the right (the more common 1929-1931 style), but only has three total positions. It can be identified by the fact that when you look down inside it from the top (as in where the spider goes into it), it has TWO little square holes (about 1/16" square) rather then one square hole like 99% of the others of that style. Those little square holes are punched out , and have a little tab punched out of them, to stop the brass part from turning all the way around. The 2nd little punched out hole is what is stopping it from turning to the 4th position. I believe these were the first style of that style of switch used in 1929 before they introduced parking lights.
Many 160 series slant cars were made before they switched to the indented firewall. I have owned 6 NON indented firewall 160 series cars.
I must admit though, that I have never seen a NON indented firewall 400A, but since they came out right when the indented foreall came out, I do not doubt that a few were made.
Steve Becker
Bert's Model A Center