How long of a beam are you wanting to make? I don't think I would put that kind load on the lift like that, it might be able to take it but I wouldn't do it personally. If your jib extends out very far it could put a lot of stress on the lift post. Also I don't think a jib would be the best setup for pulling an engine because you can't pull the engine straight out like you can with a cherry picker. You would be pulling towards the side of the vehicle since you jib is mounted on the side of the vehicle, be hard to pull the engine towards the front of the vehicle.
Personally I would make a setup that uses both posts of the lift and raises up and down by the lift. The only downside would be it won't swing or move in or out unless you make a trolley setup. A setup that mounts to your arms on both posts and has an I beam going forward with a trolley on it would work pretty good and I would think that would put less stress on the lift.
