Opinion wanted...garage hoist hookup...

I haven't looked up the engineering on this, but I can tell you that three two by twelves are incredibly strong especially if they are Doug fir. Most things are only as strong as their weakest link, and in this setup it could be the bolt you hook the chain on. If you forget a moter mount bolt, you will probably lift the whole car. Also if you are concerned about the span of the two bys, you can put temporary columns on either side or at each end of the of the car depending on which way the beam runs. This will shorten the span and make it even stronger, and help to eliminate the flex. Even just one support two or three or four feet from the wall would help exponentially.