The Suburbans have the same basic frams and the same suspension as the pickups. Yes the '73-'87 C10's make excellent donors for steering and brake upgrades. Here is one of a few threads on the subject. More can be found in the '60-'66 FAQ Index found at the top of the main page in the '60-'66 section.
http://67-72chevytrucks.com/vboard/s...d.php?t=367260
As for changing the rear axles from 6 x 5.5 to 5 x 5, you can either purchase the aftermarket conversion axles, or switch to a '71-'87 donor differential. But be aware that those will be 1.5" wider than the '60 to early '70 differentials.