Yes, thanks.
I later saw elsewhere that an outfit named Borgeson sells those type of boxes (not sure if actually Jeep or just that type of box) that will bolt on in the existing mounting holes. That sure looked like a better solution than trying to make brackets plus having the Jeep box machined as some posters did, altho - as usual - for more $.
After a couple hours more research, I did find a very good write-up complete with detailed pictures on installing a 92 Grand Am steering rack that looked to be within my capability for fabricating the brackets and the steering column extension. Also good insights on how to position it so as to avoid bump steer. The way it was done didn't position it any lower than anything else in the vicinity, and with the rack positioned offset to the left so the steering input was just inside the frame rail, it better aligned the steering shaft so that it worked smoothly with 2 joints and wasn't as difficult to install with less interference with headers etc.
Altho the write-up about the replacement box was very positive about the improved steering feel, the possibility of the rest of the links and joints being worn and needing replacement plus the cost of the box made the Grand Am rack the much less expensive proposition and, of course also gave very good results. The brackets were relativey simple to fabricate and the cost of a good used rack, or even a rebuilt, were several hundred dollars less than the cost of the bolt-in box solution, and then did away with all the links and joints & pivots exept for the tie rods themselves.
Both solutions gave improved steering feel, esp over center, and were considerably quicker. I also found a source for getting the original type box blueprinted with much closer tolerances that reportedly gave similar results except for the quicker steering ratio.