Opinion wanted...garage hoist hookup...

If I were doing this I would first bolt a 1/4" steel fish plate on one side of the sistered 2x10s end to end and then install my drop plate by taking the U shaped end and dropping it up and over the top of the 2x10s/fish plate with both tabs coming down through the ceiling.
If this is for only a once and a while use then I would just have two 4/4s, the lenght of floor to ceiling under the sistered 2x10s and temporarily install them on both sides of hoist when pulling engine, as mentioned above.
This is just my opinion, and I have been a carpenter/contractor for the past 35yrs. Mike