Getting ready to start a DIY backhalf job. Any tips?

[team39763]

I asked around the area and the easiest option is to do it myself. So I'm gonna just do it myself and see how it turns out. If it looks/feels unsafe, I'll just junk it. By the way it's a competition engineering ladder bar rear frame kit(welded frame and all).
My concerns are about having a flat/level surface. I just had a garage poured for this project, but it isn't level or flat(few dips and high spots). Is it still ok to build my frame on there, just shim it accordingly?
I bought and read a few books on suspension work. Also bought the video from Chris Alston. I bought a few tools for this job too - carpenters square, angle finder, digital level, tape measurer, digital rangefinder, plumb bobs, recip. saw, a couple grinders. I'll have a new welding machine too.