This is the specific post I would refer to within the link 65 wonton posted.
http://67-72chevytrucks.com/vboard/s...d.php?t=366850
That is specific to the '60-'62's which as as mentioned, different than the '63-'72's. The C20 suspension will bolt up the same as a C10 suspension.
On the differential, which should be a 14 bolt either full floating or semi floating, you will need to weld on a set of trailing arm mounts, and transfer your panhard bar mount from the original Eaton HO32, to the 14 bolt. When doing this you will need to make sure the pinion angle is correct. Otherwise you will have a vibration and possibly go thru u-joints. I do sell 14 bolt specific trailing arm mounts if you are interested.