I just completed this full instructional on fabrication and assembly of the LifeTrac III frame. All measurements are accurate and up to date. As mentioned in the video, we are working to further simply the process of fabricating the steel tube frame pieces by developing a simple jig to mark where the holes are drilled on either side of the tubing.
The 3D CAD of LifeTrac Prototype III is found at Open Pario. The LifeTrac page on the wiki contains further details.
Coming soon, instructional videos on the rest of the LifeTrac construction process including: loader arms, wheel motor mounts, and hydraulic system.