Update:

Today I finished the welding process and reinforcing with a 2 part urethane based adhesive

My first step was to mount the bumper, fit it in place, and reinforce the outside of the seam with aluminum tape:



This worked extremely well, because as it turns out when I fit the bumper after welding and glueing, it fit PERFECTLY. I mean, if Ford had made this bumper it wouldn't slide on and mate up any better.

Anyway, next step after taping was to prep the surface to be welded:



Then welded using the airless hotmelt urethane welder



Next, I reinforced the backside of the welded seem with a two-part urethane based adhesive. It was extremely difficult to work with and my workmanship looks like total ass, but its actually quite strong.





After letting the two-part adhesive set up, and welding the front side of the seem, I fit it on the car







Now she's ready for the flexible polyester body filler I purchased, then its sand it and off to paint.

Total time invested in this project at this point: 8hrs
Total cost of materials and supplies (minus bumpers): ~$180 ($115 for welder alone)
Price quote from bodyshop for primer and paint: $190