Jim,
Typical problem with oversized tires. Your solution is the correct one. This is exactly what we do and we even run 17" tires on some of our cars!
BUT, you will not have to make new plates, just modify the original one. Reading some of your posts and seeing what you have done...I'm guessing you have or can get your hands on a Plasma cutter?
As you can see the mentioned bracket simply extends into the wheel tub to far for oversized tires. If you cut the "middle" of the braket out. rebolt the plate to the frame, then rebolt the latch plate in place. Now you can replace the "center". Simply change the angle of the center section, weld it to the frame mounted piece first. You will most likely then have a gap to the latch side.
At this point I just use about a 1/2" wide piece of stock steel, slide it into the gap and weld up both sides.
End of tire rub! Of course changing to a good coil over set up on the rear is a tremendous up grade.
Snake: We have all been there fella, and some of us still are!
It will get better! You will get the beast done, and it will all be worthwhile!
DV