Don't remember which one, but it's one of the (many) William Higgins movies from the 70s (80s?). The two guys in the pics are using a videocam to watch three guys fuck in another room, and the brunette blows the blonde while they're watching. The blonde with the thick dick squirts a monster load (in slo-mo as was the Higggins style at the time) at the end of the scene. Always wished it was more about the blonde than the guys they were watching!
Just realised someone had answered!
So, hmm, William Higgins? I guess that starts narrowing down. But yes, I'm with you on the blonde.
-edit-
I found this place on his website :
Vintage: House One
Basically, it's (I think), all his vintage DvDs and VHS.
But he only shows the cover, and no shots from the videos
Not sure how I'll be able to figure out which one it is.