You want the jack stands under solid frame, and the corners of the frame rails, or rear control arm mounts are a good place- especially if you are going to be lifting using the jack mount.
I do recommend using a good jack- the scissor jack is really only good for emergency service, and they are weak- I've seen A LOT of bent ones.
DO NOT, I repeat, DO NOT, place your body under the car, until it is secured on jack stands. The jack alone is unacceptable for support while working under the car. A pair of ramps would be a great addition to your garage as well for this work- they helped when I put turbo sways in my 240.

I also found I needed new brackets to accomodate the new style bushings, though I got black rubber ones that came with a Volvo part # on them. The original type is cylindrical- the replacement/turbo size units have a big rectangular locating block in the middle of them, and require new bracket pieces on each side.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 230K, 88 744GLE- 220K, 82 245T-181K Also responsible for the care and feeding of: 88 745GLE, 231K, 87 244DL, 239K, 94 855GLT 189K