Identifying 1974 Topps FB Pro Drafts cards

I was wondering if someone could help me figure out how to distinguish some of the 1974 Topps football Pro drafts cards from the regular 1974 Topps cards. I know that for most cards, the Pro Drafts cards have 1972 stats on the back whereas the regular issue cards have 1973 stats.
However, I have no idea what the differences are on numerous cards that don't have stats on the back - mainly cards for linemen. Any ideas on the following?
#4 Ken Bowman
#9 Pat Matson
#42 Del Williams
#61 Rufus Mayes
#65 Gene Upshaw
#77 Tom Neville
#80 John Niland
#81 Ted Fritsch Jr.
#98 Len Rohde
#103 Len St. Jean
#109 Harry Schuh
#111 Ed Flanagan
Thanks!
However, I have no idea what the differences are on numerous cards that don't have stats on the back - mainly cards for linemen. Any ideas on the following?
#4 Ken Bowman
#9 Pat Matson
#42 Del Williams
#61 Rufus Mayes
#65 Gene Upshaw
#77 Tom Neville
#80 John Niland
#81 Ted Fritsch Jr.
#98 Len Rohde
#103 Len St. Jean
#109 Harry Schuh
#111 Ed Flanagan
Thanks!

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Current obsession, all things Topps 1969 - 1972