Hey Alex, I mentioned if before somewhere, but I just basically measured some stuff, wheel wells, etc, and transposed those measurements onto the wood. It wasnt that hard if I recall, just took a little trimming a few times to get it right. My flooring is in two sections, with the joint going front to back, in the center. There is a tongue and groove joint for the two panels, so they fit together pretty well/strong. Having the joint in the center, front to back, allowed me to install them easily and still have them contour to the body shape very well.
not a very good explanation, but thats how 95% of the stuff on my jeep is done. I just kinda measure, look at it, and make it happen... it works MOST of the time.