The one thing I remember about The Duke's other cop movie,
Brannigan, is his exchange with Richard Attenborough(?)
Attenborough: "So how's the world's second-greatest navy?" [referring to the US navy]
Duke: [Chuckling] "You oughta know!" [referring to the British navy]
As for
McQ, Al Lettieri was
the "heavy" of the early-to-mid '70s: The Godfather; The Getaway; Mr. Majestyk; McQ. The guy packed a lot in until he, well, packed it in for good in 1975.
BTW, a tip of the hat to anyone who's actually watched any of my (or anyone else's) obscure recommendations.

The unfortunate thing about some of the films mentioned is that a number of them were once pretty well known. Now, not so much. Our collective pop culture memory has become depressingly short. I thought of this when I was going to mention
The Drowning Pool (1975). It stars the great Paul Newman and his wife Joanne Woodward, not to mention Melanie Griffith, but the film, along with seemingly most of the detective genre, has been rendered obscure by the relentless passage of time.