As I recall, somebody was always trying to invent the perfect solution for this problem. We had our own idea and would put as many 35mm negs as would fit into a 4x5 negative carrier and blow the whole bunch up to 8x10. (I believe it was nine negs.)I have watched many an editor at the Olympics or World Series or NBA championship games eschew proof sheets and just eyeball the negs with a loupe, notch the neg he wanted printed and got on to the next batch. Quick and dirty, as we say in the news business.
I believe Reinhold, who occasionally advertises here, makes a carrier that holds 9 35mm frames in a 4x5 opening.