I believe you need the ball joints that are for the year of your spindles.
But we don't know what year the spindles are really for. Your spindles may be "conversion" spindles that work with ball joints for your original year truck. The tie rod connections at the spindles may be the smaller pre-1971 size on a conversion spindle as well. I think you need to read the specs on the spindles and see if they are conversion spindles or contact tech support if available. I don't know much about CPP. Others more knowledgeable than me will probably chime in. Here is a great guide from lolife99, I recommend give it a read because the answer may be in there:
http://67-72chevytrucks.com/vboard/s...d.php?t=444823