Pictures of Liberty ships show an incredible plethora of things on the deck; while many times it is just big ole' boxes, many times it is not, and in some cases it does seem like it is just a hopeless jumble. Although my Dad served on Victory ships, he said that whether the deck cargo was "neat and tidy" or not depended on what kind of mood the stevedores were in, and not on what the directions from the shipping agent or the military were - if they felt like piling a bunch of jeeps on as deck cargo, and filling up the nooks and crannies with crates of whatnot, that was what happened, and very little anyone could do about it - what counted was emptying out the warehouses and quays and filling up the ships.
About the largest aircraft I can recall seeing as deck cargo (without digging through my reference photos) is a Lockheed Hudson, with outer wing panels and stabilizers removed. I need to find that one with the tugboat jammed across the aft hatches ... I have no idea if the Liberty ship made it across OK or not, but I'm sure there were some stability problems with that load.