The only thing i see that nobody else adressed is that you said the 760 was a 1991??? The last year for the 760 was 1990....

so there's 2 scenarios... someone put 760 badges on a 740

it is a 760, but it's really a 1990 model

I would check the vin to make sure... also the model year is stated on the emissions lable under the hood on the passenger side of the car (in the US)... it will say something to the effect that "this vehicle is built to the emissions specifications for the 19xx model year"

Cliff Scott
89 740 16v