As far as i've found out in doing mine is that the bar seems to be used for locking the steering column via the ignition switch. The neutral safety switch (4-speed) is mounted so that when te clutch pedal is engaged it activates the clutch neutral safety switch and allows the car to start. The column turning is what activates your reverse lights. There are rods that connect from the steering column, on the firewall side, to the transmission so that when you put the car in reverse these rods will rotate the column and engage the reverse lights via a switch, also on the lower steering column. Hope this helps. Many people in this forum say that these Firebirds didn't have a neutral safety switch, but i beg to differ since mine has one, and has had it since built. Below are links for the backup light switch, and one for the clutch safety switch (auto & 4-speed), a schematic for 4-speed linkage, and a pic of the one out of my Firebird that's attached to the pedal mount.
http://www.classicindustries.com/fir...s/3943657.html
(Reverse Light Switch)
http://www.classicindustries.com/fir...s/c934341.html
(Neutral Safety Switch For Automatics)
http://www.firebirdcentral.com/1969_..._p/das-296.htm (For 4-Speeds)
http://www.tpocr.com/67-69linkageipc.html (Linkage schematic-See part #35)