well i dont know if this is something that everyone has or not, i heard they dont make this catalogue anymore, but when i was searching to find out exactly what year axle i had so i could do my brakes. I found this book pdf. on the 67-78 dana axles:
http://www2.dana.com/pdf/X510-8.PDF
If that link is broken, try this (thanks to dfwright)
http://www2.dana.com/pdf/X510-8DSD.pdf