I have been wanting to do this swap for years and finally the local self serve yard got a 6 lug awd astro van in. When gm upgraded the brakes on the astro van they made a knuckle with gmt800+ style brakes that bolts in place of a gmt400 style knuckle(what the astro previously used). So for $54...
www.gmt400.com
9-page thread on transferring the entire Astro knuckle, hub, rotor, caliper to GMT400 trucks. I get confused by some of the off-topic stuff--Dodge parts, Italian calipers, etc. Apparently, it all bolts up from AWD Astro to K1500 except for minor grinding on the caliper for wheel clearance, brake hoses, and needing GMT800 CV axles. Going from Astro to C1500 involves ball-joint reaming.
IF (big IF) I'm understanding this correctly, the Astro arm should work for K-series trucks, but not for C-series trucks because the ball joint stud taper would be different.
Probably worth doing the research independently. Don't trust me.