The 1520XL is your best bet. Look through the
Ork tray list as they have a lot of laser cut trays for Orks. This is what you want - they're cut really well so models will have room to be placed in the slot but not so much that they're rubbing on the foam. They're super space efficient as well so you get a lot in each tray. A quick glance told me there's plenty of trays that will interest you.
I use a 1520XL for my Tyranid army, and I couldn't imagine trying to fit that many big and awkward and small and awkward models in any other case. It's a pretty awesome case as long as you know what you're getting into regarding the size of the thing.