No spring compressor needed dude...consider the fact that the block of wood on the gas tank advice came from someone who is a first gen. wrench, & was passing along the advice from someone who calls themself SPAZZ...if you can't figure out whats real, well... I got nothin' more to say...except, always jack on (not off) solid lift points, like frame or axle, & ALWAYS use jack stands.
Also, if you have jackstands under the frame, you can move the axle up and/or down with the floor jack to facilitate (nice wurd eh?) alignment of lower shock mounts.