Yes, it will fit. You will have to source the bumper, rebar, bumper mounts, and cushion. You will then have to remove the rear bumper shocks from your 7-series wagon, and install the aluminum bumper mounts from the 960 rear bumper. The 960 rear bumper will then bolt right up. You may have to open up a couple of the holes on the aluminum mount pads with a round file or Dremel in order to get it to fit right.

The front end of a 960 will fit on a 7-series as well, but it involves a bit more work.

I'm sure the basic dimensions are similar so the project can't be too bad.

It won't be a "bolt-in" however. The newer 960 & S/V90 vehicles have a different bunper system. Rather that the "shock-absorber" mounting system on your 740 the newer system incorporates crushable material under the bumper pad and crumple zones in the frame with no shock-absorbers.

Post a picture if you do it or find someone who has.
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'96 965 with 16' wheels at 118K. Had '85 745 Turbo Diesel for 200K.

I know this doesn't answer your question but it might be a ray of hope. I saw a 740 sedan for sale awhile back and it was advertised as having an S90 upgrade. Bumpers from the S90 were nicely installed on a 740. I thought it looked peretty good so, as I say, maybe there's hope.
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Roy Olson