Is all your transmission to steering column linkage intact and not bent, or otherwise binding when you move through the transmissions manual valve lever while the floor shifter cable not connected? No headers, or some other modifications made to the linkage in anyway?
I would disconnect, or at least loosen the lock bolt that holds the rod from the steering column on the frame to trans linkage (see pic below, it has wave/spring washer), then work on the cable adjustment from the floor shifter to the transmission control lever first.
Get your lock nut and pin for cable in the proper location in the lever's slotted arm (see second pic below, circled in red). Service manual wants you to put shifter in PARK, the transmission lever bracket in PARK position, then put the shifter cable's transmission end pin into that slotted groove, and tighten.
Once you have it working properly from the floor shifter only without the column linkage possibly binding you up, then go back and adjust your column linkage and re-tighten that bolt (with the wave washer).
When you're done be sure and check for your REVERSE lights to come on when shifter is in R, and make sure you can't start engine (turn key in IGN) unless your in P or N on the shifter.
There really isn't a lot to it, but there is the two adjustments you have to deal with if it's a floor shifted setup with cable so you have to get the one adjusted first working correctly, without the other interfering...then adjust the other afterwards.
You won't have steering column shift lever, so that's why you have to get the floor shifter, and cable adjustment set up properly first. You can grab the outer shell of the steering column, below the IGN key cylinder and rotate it left and right. It's the part that you can see turn when the floor shifter is moving between gears. It's the part that also moves the little PRNDL pointer in your dash, FYI.