Engine out can I install Dougs beforehand

Yeah that's it.
If you put the engine in first, you will have to push the T-bars out to the back, and pull the column out, in addition to dropping the steering and oil filter.
If you try bolting them on with the engine above the frame-rails, well, that just will not work.
mguner nailed it.
You are sorta on the right track tho. Just before the engine drops onto the mounts, it is sometimes possible to hang the passenger side loosely on the studs.But with the T-bars and column in there,I usually drop the mounts into the K just far enough to not pop out, as I suck the tranny up into the tunnel against the floor(yeah that means the tranny is pre-attached and I have an engine tilter). Then with it so set up, I spend the rest of the weekend trying to get the drivers side on, and the motor down somehow all at the same time.
Ok so all exaggeration aside it is a lot easier with at least one Tbar slid back, or the column out. If you need to roll the car back and forth to marry the tranny, then column it would have to be. The column comes out pretty easy; 3+3+2+1. 3bolts up,3 bolts down,2 wire connectors, and the roll-pin at the coupler.
OOps 68s had just 1 wire connector IIRC. After you've done it once, you'll be taking it out every time you need to change a dash-bulb, and be wondering why you ever avoided it for so long.