want to buy 62-70 b body 8 3/4 rear end
You don't want the early splined axles. And the chart you probably got the 62-70 reference from is a POS. they aren't the same widths for that range of years.
Ideally, find a 65-67 B body rear, it's slightly shorter than the 68-70 rear. Here's a good reference for rear end widths.
http://www.moparts.org/Tech/Archive/axle/16.html
Might try putting this in the wanted section.