Go to Northern Tools and Harbor Freight websites and look at their engine stands. There are four wheel models that are unstable and four wheel models that are much more stable.
http://search.harborfreight.com/cpisearch/web/search.do?keyword=engine+stand&Submit=Go For safe, general-purpose use, I think that the Harbor Freight 2,000 lb-style model is safe and worth the extra $ over the 750 lb model (it might still be on sale in their retail stores). Similar leg/wheel designs are available at other vendors.
AS Houston54 stated above, the 4-wheel 1,000 design is much better than the 3-wheel 750 lb design.
Tim
