Post #11: 

I've been slacking with doing an update.  As of 10/20/2016, I've been able to do a few things since buying that F100.

I welded in a c-notch in the rear, although I won't cut out the inside pieces until I square it all up and after I install the future trailing arms with the original axle.

Here's a couple of pics of welding in the c-notch (nothing too exiting):


I cut a notch out of the motor crossmember (in order to lower the small block Chevy V8 within the frame to clear my hood).


Afterwards, I bent up some 1/4 inch steel to re-enforce the notched crossmember and welded that in (I know my welds look harsh....but I was using CO2 as my shielding gas....it penetrates deeper but welds ugly):

Next, I boxed the frame in the area where I plan on welding the trailing arm crossmember (in these pics below, the crossmember is merely mocked in place):

But, before I can weld in the trailing arm crossmember and set up the rear end, I have to weld in some motor mounts and fab up a transmission crossmember.....so that's what I'll work on next...