How tell difference between a 69 and 70 rear end/axle?

[scottv]

I'm looking at getting a 5-lug conversion kit to change my current 6 lug rear to 5 lug. But it looks like there is a difference in kits between a 69 and 70 year rear end. My truck is a 70, but I'm not for certain it's the original rear so I'm wondering if there is any easy way to tell the difference between a 69 and 70 so that I order the right conversion kit for what is on the truck? Thanks!

[tcoop68]

If you can find a 71 or 72 rear end they are all five lug . It's easy to swap rear ends.

[CC69Rat]

Lay under the back of the truck and have a buddy hold one end of your tape measure against the back side of one brake backing plate. Measure to the same point on the other side..

Inside-to-inside the early housing will be 55.5" long. The later housing will be 57" long.

Early axles are 30.5" long from the wheel mounting surface to the end of the splines. Late axles are 31 5/16.