I reckon you would run out of cubic metres before you reached its mgw TBH, a 20 foot container has a max gross weight of just over 30 tonnes.
That would be alot of Deltics!!
Weight per pallet would be interesting, dare say somebody would know, as you say, they are heavy models.
Selling my American H0 loco's in the past, I've noticed that an Athearn Genesis SD70 in its large box, similar in size to the ones Accurascale is using for the Deltics, brings it close to 2KG!!
They cost a fair amount to post.