I am in the packaging and we NEVER use styrofoam for any sharp or pinted objects. One drop and the styrofoam crack and migrates around the box losing all integrity. Use 2" thick 2# polylaminate foam and you will never have an issue. FWIW.
Frank

I use a cooler for me it's the way to go. I fill the voids with expanding foam but I shoot the foam into plastic bags so then nothing sticks and the bags form around the parts perfectly. I never had a problem with shipping damage so far. I've shipped trannys and cases this way.

I once received a pair of -previuosly immaculate- Solex camshafts from a guy in the US solely packed with a standard USPS box without any (sic!!) inner layers or protectors.
One broke apart and smashed all sensitive surfaces of the other one.
Brilliant guy, great job. :-(