Basically, you got to get the new heim's threaded in as close to the old ones as possible. If you don't, you can move the spindles closer (or further) to the transmission causing the axle to bottom out, which will cause either the spindle to break or you rip tabs off the frame. (Ask me how I know lol ) or if it's too far, the axle will pull out. Your alignment will get whacked as well and your rear end will be all over the place at speed.
Lastly, you need to double-check axle length when you're all done to make sure. It can be a real mother to adjust those five links.
I think he's going to find that each side isn't the same.
If I were to do it all over again, I would swap out all my heims, get the rear as even as possible, and then aligned... then measure for new axles last. When you're using the old axles you kind of have to work around those measurements. Some of my heims were almost threaded all the way out on one side to get the alignment correct.
If his car was set up properly from the get-go he probably won't encounter the problems that I had.
