He wont have to drill holes. They should already be there on a 73. They stopped putting them in the frames after 82 when 2wd was no longer an option on a K5. You will have to cut the rivits holding the 4wd stuff on, and the whats holding the 2wd stuff on the other truck. It should be a bolt on after that though.
This is what I have been able to find as I've been researching my swap. I have an 87 I'm converting to 2wd.
See this thread for reference:
http://67-72chevytrucks.com/vboard/s...d.php?t=168231
This is an 82+ truck as well so he had to drill the holes too. My build thread is in my sig, but I havent started the suspension swap yet.