I am currently installing a 12 bolt rear end in place of the factory 10 bolt I want to know there two support bars that tie the upper control arms to the lower are these nessessary to reinstall i have been having trouble getting them into postion. the one end mounts up into the back side pocket of the upper rear control arm and then mount to the lower control arm. I would greatly appricate if someone could help me out with this problem Thanks

You don't HAVE to use them. Many chevelles didn't have them. But, I think most people with performance oriented chevelles would recommend using them. They help strengthen up the control arm mounts. My 68 didn't have them, so I added the Hotchkiss tube braces.

I think the factory mostly used them on the high-perf cars, and cars with 4-speeds. Aside from the installation effort, there is no real downside to using them - only good! :)

When my mechanic installed my 12 bolt he sold me a set of the Hotchkis braces cheap. I like them they help triangulate the rear suspension. Hopefully someone on here has some pics to help you figure out how to mount them.