I've used a chain on dozens of them. The only issue is don't use a chain that is too light and don't hook to bolts that are too small especially ones that may be in shear.
I've seen a couple of under sized chains (actually the results of) break and I have seen a chain with a previously damaged link break so one needs to use a properly sized chain for the job.
I've also seen bolts that were in shear break but that is usually when the bolt is too long and the chain is loose on it or the bolt is too small to do the lifting in shear.
I used an engine lifting chain similar to this one
http://www.northernautoparts.com/Pro...ctModelId=5567 for years in the school shop I taught in and that style works well. Google engine lifting chain and several examples show up.
My preference on the six would be to use the head bolts or use slightly longer bolts in place of a pair of head bolts with the above style chain.
I'm not too found of the strap around the engine Idea as I think you might not have full control of the engine when it is lifted. Ok for an old engine going to scrap but I don't think it would be the best for trying to install one in a truck.