Scott Stamps 735A And 768A (Byrd Expedition)

I am trying to determine whether a single imperforate stamp in my collection is Scott stamp #735a or Scott stamp # 768a. This issue was considered by the Forum back in 2013, but the link to an article describing the different "Farley's Follies" stamps is now corrupted - do not click on the referenced link!
One commentator in 2013 (rohumpy) concluded that "it is not possible to differentiate a single sheet of one from the other" [i.e., 735a and 768a].
Is this the consensus opinion? I understand that 735 was issued in panes of six stamps, while 768 was issued on larger sheets - but of course once these are cut into single stamps it becomes difficult or impossible to differentiate between them.
Also, is there an updated link or other resource that sets out the differences between the various Farley's Follies stamps?
Thanks in advance for your responses.

Use SCF search button and search "Farley" for many returns. In general to tell the various imperforates is with and adequate margin which can only come from the special printings.

Did you find your answer? Parcelpostguy is right, to be sure it is the 768a, the stamp needs to have a margin that is wider than the normal margin on the 735 souvenir sheet.
Here's mine. Notice the wide right margin on the 768a single, and the wide left margin on the 768 sheet.


Similarly, a single with a gutter or straddle margin showing parts of an adjacent sheet would also identify it as from the Special Printing.


The one that still stumps me is the perforated Byrd single 733 vs 753. No way to tell as far as I know, except for the unused single, with gum, it is 733, but a used single or unused NG is indistinguishable. Fortunately the mint catalog value is the same, although inexplicably the used Farley special printing is just 45 cents while the original 733 used is higher at 50 cents. Go figure.