I will go by division & let you decide. In the late 70's the QB position was so deep, that the back-ups could easily be starters in most cases. Also, the youngster who took over for the old pro kept the offense moving (business as usual) There are also a few dogs in there (Detroit...WOW).
*COULD START IN MULTIPLE ERAS
AFC WEST
OAKLAND RAIDERS- *Darryl Lamonica/*Ken Stabler
San Diego - *Dan Fouts
Kansas - *Len Dawson
Seattle - Jim Zorn/Dave Kreig/Steve Deberg
Denver - *Craig Morton/*John Elway
AFC CENTRAL
Pittsburgh - *Joe Gilliam/*Terry Bradshaw
Houston - *Dan Pastorini
Cinci - *Ken Anderson/*Boomer Esiason
Cleveland - *Brian Sipe
AFC EAST
Miami - *Bob Grecie/*Dan Marino
New England - *Steve Grogan/Tony Eason
New York - *Joe Namath/Richard Todd
Buffalo - *Joe Ferguson/*Jim Kelly
Balitmore - *Johnny Unitas/*Bert Jones
NFC WEST
49ers - *Joe Montana/*Steve Young
New Orleans - *Archie Manning/Bobby Hebert
Los Angeles - *James Harris/Vince Ferragamo/Pat Haden
Atlanta - *Steve Bartkowski
NFC CENTRAL
Tampa Bay - *Doug Williams/Jack Thompson
Green Bay - *Bart Star/Lynn Dickie
Minnesota - *Fran Tarkington/*Tommy Kramer/Wade Wilson
Chicago - *Vince Evans/Jim McMahon
Detroit - Eric Hipple/Gary Danielson
NFC EAST
Philly - *Ron Jaworski/*Randall Cunningham
Washington - *Joe Theisman
St.Louis - *Jim Hart/*Neil Lomax
Dallas - *Roger Staubach/*Danny White/Gary Hogenboom
New York - *Phil Simms/Scott Brunner/Jeff Hostetler