Thanks for all your replies.
My plan will be to cut and fit all the patch pieces and the left strut, figure out where the welds will be (I have an air Flange/Punch tool and use it were appropriate), use weld through primer where the laps will be and weld in the patches. Since it is not the body, I'll either weld the laps along the edges or punch holes and plug weld. I'll use the POR15 Prep & Ready on all the new steel and paint everywhere except where the welds will be with POR15. I'll prep and paint the inside of the strut the same way, use weld through primer on the "flanges" of the strut and plug weld it on. Now, with it all together, I'll prep then POR15 the new steel and extend the POR15 onto the surface rusted metal.
In spite of having painted the inside of the strut, I'll drill a small hole and spray something like Waxoyl into it.
There is some surface rust on the inside of the fenders and the floor so I'll scape back the existing undercoating to shiny metal (I have done a little of that already and there IS shiny metal under much of the undercoat
). I'll POR15 all that and follow it with undercoating.
Work will keep my busy for a couple weeks, but I'll ad pics as I progress.
Thanks again,