Aidan;

Front Xmember and rear diff are always garanteed safe to use when using a floor type jack (they danmwell better be, if its still a roadworthy vehicle!). If you only want to lift one corner, the suspension is next best. Last choice is to jack at the junction of the longitudinal and transverse (yeah, the ones that turn to dust) "frame" box sections only after you've determined they're absolutely solid, and then ONLY by using a block of wood to spread the forces...as you know, being of unibody design, its only sheetmetal there, so you sure would'nt want to concentrate the entire vehicles weight on a small area. The OE jacking points are quite strong located as they are, but ONLY if you're using the OE screw jack and its unique hook and lever attachment.

After lifting, use jackstands to secure before doing any work underneath...accidents suck, and can ruin your day...be safe!

Cheers