AMEN on the cinder blocks!!!!  Years ago I spent the better part of one morning UNDERNEATH a 1962 Corvair taking the engine, transmission, and rear suspension loose so I could pull it out as a unit.  After getting everything out from under the car I leaned against the car to take a well-deserved rest.  All at once, one of the 4 12" blocks I had the rear of the car resting on crumbled and within a second the shifting weight busted the other three.   Standing there looking at that car sitting flat on the ground (and I do mean flat on the ground . . . as in the rear part of the floor made a dent in the ground and the lower rear apron was buried a couple of inches deep) I realized why my dad had always preached "PUT IT ON JACK STANDS, SHAKE IT AND SEE IF YOU KNOCK IT OFF OF THE STANDS . . . THEN, AND ONLY THEN, GET UNDER IT!"

This isn't the first time this has happened locally either.  A couple of years back, a mechanic here in Chattanooga was working under a Taxi and it fell and killed him.  It's one of those things that you might do millions of times and not have a problem . . . but it only takes once to kill you!