If your spreader bar under the tank cover has not been modified all you need it the cast bracket that mounts on top the tank cover.The original spreader bar has the support for the bracket.Those brackets appear quite often in the classifieds or that auction site.
Here is one.They are 3 listed
https://www.ebay.com/itm/16626024482...Bk9SR8rWjM7IYg