You can get those units onto the island via Sea Cap, but you do need to have a port on the island to do so. With the converted LST ports as well as the others nearby the historical invasion spots, that shouldn't be too difficult. Of course, that is then going to cut into the amount of supply you can send to the island. Ah, decisions, decisions...
I've read the response here and on CSW and I can't find anywhere in the rules that says this.
CSW refers to 1.4a allowing it.
However, 1.4a says that you can use naval transport, it doesn't say that you can use shipping capacity.
Ok.. just checked the errata for Sicily II, that one line in it makes so much difference.
"off map boxes have ports"
That combined with 3.2a is what gives the ability to use Sea Cap.
(I think... :-) )