ipd sells a little leaflet/booklet that explains a few things. in short, the anti-sway bar counters the chassis's normal motion of leaning to the outside of a turn, hence the car goes around the turn flatter. sin is right, because u are essentially making two independent suspension tied together, u will lose some ride quality, but not that much. on the front, it is commonly shaped like a butterfly clip and connected around the same plane as the wheels (as opposed to tower braces which usually connect above the engine compartment).

almost all 850s (can't think of any that don't) have some sort of front anti-sway bar, differing only in thickness on different trims/models. some 850s have rear sway bars, others don't. most turbo sedans have both, while some turbo wagons do and others don't.

as for fitting a 850 bar onto the 940, no. two very different platforms. 850 is fwd, 940 is rwd. the front suspension is vastly different to help the 850 accomodate all those drive shafts and what not. u will have to get a set made especially for the 940.