Just remember the 70-72 rearends are 3/4" PER SIDE wider than the 67-69 rearends.
I would still buy new axles from Moser Engineering to replace those old axles.
$260 from Moser Engineering.
http://www.moserengineering.com/axle...spline-31.html
Summit Racing sells them.
http://www.summitracing.com/parts/msr-a3065gmt5