Ididit makes a 68 only tilt column that bolts right in. I have one in my 68 and am very pleased with it. It's also a bit shorter than stock and moves your hands closer to the dash. I used a Grant 14" diameter Corvette specific leather steering wheel.
Sent you a PM about the Ididit column. Just looked on ebay using 1968 corvette steering column and found 6 of them. One is under 500.00 and the others just over. You can also go chromed or raw and paint the column to match your interior.