Need 12 Bolt Info

[chevyrestoguy]

I'm pretty certain that when they changed the bolt pattern to 5x5 in '71, the rear end width increased 1.5" total, and that width was unchanged all the way to 1987.

Options:
1): You can buy 5x5 "conversion" axles for your original rear end.

2): You can have your 6 lug axles redrilled for 5x5, but it really weakens the axle flange. The end will look like swiss cheese.

3): You can't shorten the stock 5x5 axle to work in your '66. The 12-bolt axles are retained with c-clips, and if you shorten them to fit, you have to machine off the section that retains the c-clip. Sure, you could probably have the stock axles cut, resplined, and machined for the c-clip, but after all that was done, you'd be better off buying the conversion axles.

You will need the entire rear brake assembly from a '71 to '87 half ton. I would suggest finding a heavy duty set-up with the wider brake shoes.