When I did mine I had a 74 truck column too. Working from memory I think it was at least 2 if no 4 inches longer than the 82 eldorado one I used. It was long enough that it interfered with the ram horn manifold and head. If you are running a six it would not be an issue. If you look at the photos of the cable shift linkage at the firewall in my thread, and imagine the column longer you can see the problem, especially if you are using the column shift.
http://67-72chevytrucks.com/vboard/s...&postcount=134
You can shorten them but it requires complete disassembly and good welding skills because you have to cut and reweld the shaft. I would use a column of the right length before I would trust one that had been cut and rewelded. Once you get it put back together there is no way to check for future problems.