I concur, the crossmember directly behind the oil pan is the way to go. I put a piece of oak 2x4 about 12" long on the jack to distribute the load over the entire crossmember. Once up, jackstands go under the jacking points and away it goes.
As for the rear, the differential housing is your best bet. Once again, use a good piece of wood (something soft so it gives a bit), jack it up, and then put your jackstands under the rear jack points and your're good to go.