The wiring can be used between the two columns. The wires are different colors on the connectors but do the same thing so I'm keeping the harness from the Y88....It's in better shape than the 1977.
The ignition switch that is mounted on the lower columns are also transferable.
But.....you cannot use the same column tubes/jackets. They are different sizes, along with the inside tube and shaft.
The seals at the end of the shafts, towards the firewall, are also different.
Everything else can be swapped once you get past the tilt section.
Here is the link that helped me do this project......it is spot on with the disassembly....And some help from the many videos.
http://www.buickperformanceclub.com/tiltsteeringcolumnwobble.htmThe mounting plate at the firewall end of the columns are the same. The one on the tilt column is a bit rusty so I'm going to take the one off the Y88 column and weld it to the tilt column.
If this is something you want to try, for the tilt column, watch out for the upper and lower bearings. There are 14 little balls on each bearing and once you start tearing it down they start dropping like flies. Luckily I was able to find all 28 little bastards. They hit the floor and can bounce several feet.