Didn't even need a welder. I had a sheet of black plastic laying around (I salvage old backpacks and luggage) and realized the only part of the shroud that came close to the new fan was in the corner where the depth of the bump on the top wasn't enough. See attached photos. So I could cut that section off, move that piece of the shroud towards the radiator, rivet, then add my extra piece of plastic and rivet that too. It works fine.
Where the new fan gets too close
I cut along this line. I found using a reciprocal saw with a wood blade worked best, but made some mistakes along the way.
Cut off piece moved towards the radiator, then the new strip of plastic added.
It works.