Ditto on the leaving the column in the CCW position and it will be fine. Did my T56 swap 8 years ago and never had a problem with it moving. Remove the lockout arm at the end of the column for appear sake and it will also remove a little weight which will try to rotate the bowl.
Mark Hichens has good info on his site about manual trans columns. http://garage-scene.com/t5-into-ag-body/
G-body tilt/manual trans column donors are very rare and the only rear advantage to it is you can say you have a manual column in the car. It's one of those things I didn't do but it's on the "to do" list for this decade.
IMO a neutral safety switch is a must, easy to do. You can adapt one from an F if necessary. The stock G switch has been unavailable for years. Bought my GM switch from The El Camino Store years ago when they still had a few left, should have bought every one they had at the time. No one but me ever drives my car but without a neutral safety switch someone can try to start the car and destroy the front end. I've saw that happen once at a shop.
For reverse lights use #12085485 factory pigtail with has the plug for the reverse light switch. From an early 80's Chevy pickup with manual trans pull the underhood reverse light harness from it. It will have the correct wire coloring, a grommet, and the correct plug which will plug right into the Monte plug under the dash, very clean and simple install. Pics if you want.
I know this is for an LS install but as 85SS stated a CCC stick car needs to be wired so the CCC thinks the car is in drive all the time. You simply remove the ORG/BLK wire from the gear selector switch so the CCC see an "open" all the time.
If you decide to install cruise you should install a cruise cutout on the clutch pedal, just more cheap insurance, unless you have a rev limiter set at about 4K. I did make that mistake back then when I did the T56 install, no way can you shift with the cruise on, good thing it was the old 305. To install the cutout you just duplicate what is on the brake pedal, putting the switches in series. The biggest PITA is you need to weld a small tab on the bracket under the dash that the pedal are mounted to. Pics if you need them.
Putting a T56 in a car will change it personality drastically for the better. The clutch/linkage/hydraulics is what makes or breaks the install in regards to drive-ability. I've driven six G body stick conversions and they range from very good to extremely poor. Choose a pressure plate like you would choose a cam, if you ain't going to race it with slicks don't put a clutch in that handles 800 ft/lbs. The smaller the disc you use with a T56 the better the trans synchros likes it, called "spin down time".
Reverse lockout on a T56 is a done with a solenoid. A factory T56 car uses the PCM to open the gate below 5mph. The shifter can be made to go into reverse by forcing it through the spring loaded gate, not a good idea according to the T56 venders. Houlie has a button on his shifter to open the gate, a momentary switch. Initially I used a lighted rocker switch on the console to open the gate, not a good idea. Had to add a buzzer to that circuit to warn that the gate was open, that made the lockout "idiot proof". Hopefuly the PCM that will run your LS will have a connection option for the lockout.
Always try to get the T56 as high in the tunnel as possible at the tailhousing, helps the driveline angles. On a Gen 1 SBC install this seems to be a common problem, trans sitting to low in the rear. Not sure how an LS/T56 swap would be, just try to get the tail up.