I can tell them from the front headlights... The 740's had either those
sealed beams or one big wide lense. The 760's have "old 960 style" front
lights: thin middle mounted fogs and then big square main headlights... The
whole front end looks really narrow IMO on these cars.
If the 740 and 760 are old enough, they both have the sealed beam lights
tho... But I think that was pre 1986/87ish cars.