Back in the old days, we all used to get 2 snow tires for the drive wheels.
These
help get you going in the snow, but they don't do much to help your stopping
power on snow and ice.  I don't remember, but I don't think the 91 740 had
ABS brakes, which also help.

Winter tires now have a layer of soft rubber on the exterior tread which gives
much better grip on ice, both starting and stopping.  A set of 4 lasts about
3 seasons, and then the outer layer is worn off, although they are still good
for non-winter driving.  Beware of buying used winter tires, as they may have
no more of the soft rubber left.  I have a 98 XC, and the winter tires make
a huge difference, even with all-wheel drive.

There is a lot of info at www.tirerack.com.  I don't work for them, but I have
bought from them.  They post some comparative tests (stopping tests on a
hockey rink!) that are interesting.

I have a '91 940 (essential the same car as the 740) and for years I've been
running Dunlop Wnter Sport tires I buy from Tire Rack.  I use 4 snow tires
and have found these to be excellent in snow, wet pavement as well as dry
pavement at high speeds.

Nokian or Gislaved, both aren't overly cheap tho. I've head Hankook snow
tires are good for the money - no experience with that particular brand tho.

I bought a set of Pirelli Winter Carving.

They seem to work well in icy conditions.  I've only had them on my 760GLE
for a week, and it has only snowed once, and not badly enough to see what
they are like.

They are quiet, and don't give the best traction in dry conditions.  The car
feels like it wanders in the lane at 120km/h, at 100 it is better.

I paid $100 each installed (Cnd$) for the tires, a 2nd line from a no-name
wasn't any cheaper.

I am happy with them so far

Size: 185/65/15 on steel wheels, Pirelli Winter Carving