Yessir, you sure can. This isn't scientific or by the book, but it has worked for me:
On top of your steering box there is an allen head screw with a lock nut on it. This is what you will need to adjust.
Park the car on a level, solid surface, like a garage floor.
Stand outside the car, move the steering wheel gently left and right while watching the drivers side tire for movement. See how much travel is in the wheel before the smallest movement of the tire.
Loosen the jam nut on the slotted screw. I think you will turn the screw to the left (CCW) to tighten up the box. It won't take much, just a turn or so.
Move the wheel again to see if the slack is out of the steering. If not, again turn the adjusting screw, until you barely feel some resistance in it.
Check steering again for slack. If it seems right, tighten the jam nut securely.
Take it out for an easy drive around some corners and see how it does.
Be very careful not to over tighten the adjustment screw to the point that you can feel any binding in the turns, and the steering wheel should re-center itself after a turn.
This will be an excellent time to pull one of the bolts out of the steering box top cover, and grease the steering box. Don't use a gear oil, use a grease gun.
As far as the "floaty" feeling, get a good front end alignment. Check this forum for specs, but DO NOT leave it up to the alignment shop to use the old specs from 66. They are set up for old technology tires. If you don't have radial tires, get them. It will make a HUGE difference in the way the car steers.
