I would just put a piece of square tubing across two of the arms. Use clamps or bolts to hold it in place and wrap a short chain with a hook around the tube. One time I hung a 350 small block/turbo 350 combo from a rotary two post lift by just running a chain from the arms on either side.
It would certainly handle the weight of an engine or even an engine/trans combo. But the overall lifting height would be an issue. The lowest part of an engine or engine/trans would have to clear the car and depending on the engine, the top part may be over 6 feet high in order to get it out of the engine bay.
Then you have things like the hook, the attaching chains, and the lifting bar itself to add to the height above the engine.
The lifting height will be an issue. Unless you pull the front clip, you wouldn't be able to get enough height to pull an engine. You could build a frame with uprights on both sides and mount it to the arms next to the posts. This would also give you more clearance as the arms could be folded out of the way, and you could use the full range of the lift vertically.
I have a Mohawk lift and have used it to remove a truck bed ,but an engine...........
I bought a folding 3ton engine hoist/crane on Craig's List for less than $100.Much better.Get a leveler too (HF)
What kind of car do you want to pull the engine on? You may be able to drop it out the bottom and use your lift to lift the car above the engine your pulling. Lots of newer cars can have their engines removed from the top or bottom.
I had considered doing this with my 2 post Rotary lift. I was considering fabricating legs that would attach to the lift pads and connect to an I beam above. It would basically be a gantry crane with short legs.
After I thought about it a while, I ended up making a separate full size gantry crane that works independent of the lift. It made much more sense for my situation.
We unload engines from the back of truck beds with our lifts. Throw a sling around the arm, hook it to the engine support hook or a bolt, and move the lift up.
Of course if the forklift is in the area we just use that, but sometimes it is buried.