All GM trucks '87 and earlier came with solid front axles.
I would start with centering your Dana 60 in the front wheel opening, set your springs in place and see where the front hanger needs to be. You might also look into some of the components made by Kert at DIY4x. He makes a 52" conversion for the '67-'72's that should fit your '66 with minimal if any modification.
http://www.diy4x.com