When do you need rear conrol arms?

[fiveohpatrol]

The easy way is to just weld up the seams. The best way is to buy a re-inforcement kit and weld that in. I believe wolfe racecraft sells one. A friend of mine made mine for me.
Pinion angle can be measured a few ways, but here is a link for it:http://baselinesuspensions.com/info/pinionangle.htm
Take a look through that site, you'll learn a ton about suspension geometry. Enough to make your head hurt

The uppers mainly control the pinion angle, and the lowers compensate for any difference in lenght that you make the uppers so you can keep the wheel centered in the wheel well.