I'm building the Prusa I3 box frame version and there are different rod lengths mentioned on different sites.
What are the definitive lengths if I have the default wood sizes?
6x 450x100x12mm wood
1x 475x100x15mm wood
Also are the 3d printed parts different from the single sheet frame?
And how do you correctly attach the z-axis to the wood, at what height should you mount the motors?

First of all I do not recommend wood frames. They often bend and twist and give you z-wobble and other artifacts. If you can afford it get a P3Steel frame. Look up P3Steel on the Wiki and you can find anything you need for such a build. My original frame was wooden, gave me all sorts of problems and finally broke. I quickly upgraded to P3Steel and my problems disappeared.

I have a tight budget. I dont have the money for a steel frame.