Karl;
GOOD and interesting find, there, Pard! It does look like the rack was possibly assembled from either small-diam pipe or maybe large re-bar type stuff. (As versus those racks we've often seen and sometimes modelled built from metal strapping or strips). From the pic, it's hard to determine how exactly the elements were joined, though I would suspect they were welded?
The profile of your rack looks pretty good and appears to match your ref pic nicely - but the key elements of HOW it was attached to the tank obviously remain to be found or disclosed!
I would bet that there were either some welded-on plates (feet) on the rod-ends for bolting or welding to the tank, or maybe even an additional base member running the length of that rack to tie rod ends together? Leastwise, that might be the approach I'd consider!
This will look GOOD!
Bob