Thank you guys but I am looking for exact FORD info (as in a service letter).
These are not so-much spacers but reinforcing rings/plates to prevent the thinner 1957 flex-plate from center shearing. It seems to me also that the flex-plate should be sandwiched with the minimum of one ring @ the CS flange and the other two @ the outer side on the plate.
The placement of these rings will also assure correct placement of the convertor assy to the front pump and possibly the RG to the starter drive. This is a 1957 design retro-fitted to the previous years 1955/1956.
There may have been a SERVICE SHEET in the original B7A 6375-A for earlier retro-fit. Most likely it was a SERVICE LETTER advising of the change and proper assembly.
An aftermarket kit most likely would not have included that info (IMO)
1958 flex-plate showing center hub tear-out.
W (BY GOD) V - EASTERN PANHANDLE