My son-in-law, Blaine, fabricated a fan shroud for my '34 Ford coupe. He began by shaping a steel rod over a wheel rim to form the shroud opening. He temporarily tack welded washers to the rim to locate the shroud opening. He then used 1/4" steel tube for a frame base and built a spider ring. Mock up and check for fit. Sheet metal was cut, shaped, and welded to the spider ring. The fan shroud was mocked up for a final fit prior to grinding welds and painting. A flat black paint job completed the project.
That ought to work! Nice job and the fan looks to be in the right place with the blades centered in the hole front to back.