Your project sound interesting!
Although there are many drawings of striker castings in the SRHA archives, they typically only show a casting number, not a patent or vendor. The Southern cast many parts at its Lenore Car Co. foundry in Lenore, TN. I expect many were copies of carbuilder designs or designed by Lenore or the railroad. Producing parts at Lenore and sending them to the carbuilders to be used in new car construction was common so even knowing who built a particular series of cars does not tell us who the component suppliers were.
In any case, here is a Google Drive link for Southern drawing SF-3421:
It is a 31M .tiff file (too large) to attach here. You should be able to read all of the measurements if you want to try to use this design.
Good luck and let us see how this looks in proto:48>