Happy with that the mockup frame profile would work, four identical steel copies were cut to start building the new rails from.
Four new profiles cut and ready to graft into the frame.
A view of the outer splice on an angle. Also the top and bottom cuts are offset so there is not a continual seam around the frame rail. The inner frame profile actually had the angle splice leaning the opposite direction as well.
Lined up the passenger outer rail profile and prepared to tack it into position.
Strips the correct width of the frame were cut and formed along the top and bottom of the side profile. These along with the inner rail side were carefully fit and positioned correctly and tacked along the edges.
Passenger side finished to that point, starting driver side in the background.
View from the rear
Both new frame rails are now assembled and tacked.
Now that the rear frame rails were built, all remaining crossmembers in the frame were removed. After that the rails front to back were checked multiple times for square and accuracy.
After that, full length templates were made from the rear splice all the way up to the front suspension crossmember. With an accurate template, new steel boxing plates were cut and tacked into position. This really stiffens the chassis up, cleans it up visually and aids in installing components later in the build.
View from the side showing the full length of the frame now boxed. Also note the front splice behind the front suspension crossmember was also done at an angle
View looking down the length of the driver side frame rail