He answered question 1 himself, he needs question 2 answered, which I tried but I'm not up on AD columns.
I hope somebody is able to answer Question #2 for later than 1953 trucks. "Can I use/swap the steering column with my 49 panel?"
He did not answer question #1. "what year the AD trucks had factory turn signals?"
GM (the factory) had accessory turn signals for trucks well before the 1954 accessory turn signals.
My guess for question #2 is that the 1954/55 steering column should be able to be swapped in (maybe bolting differently under the dash). Maybe someone knows if the older steering wheel would bolt onto a 54/55 steering column. The 1954/55 turn signal "cup" and signal mechanism parts would not match up as they door to the underside of the 54/55 steering wheel.
