Head over to www.67-72chevytrucks.com . There is a 60-66 forum and they can point you in the right direction.
Try: http://www.ecklerstrucks.com/dept.asp?dept%5Fid=362 or http://sfbay.craigslist.org/nby/pts/780818004.html or http://www.wscmotorsports.com/catalog/gm/trucks/6066gmtruck/6066gmtruck.htm