Rick:
I can help you more once you have a ship name, but getting that name will be difficult. The National Archives destroyed the pertinent shipping records quite a while ago. I
Perhaps the best start would be to request the UNIT RECORD CARD for the 505th from the National Archives. That record will have a great deal of information about movements...and may include the shipment number or the name of the ship.
One way would be to request a list of unit records from NARA regarding the 505th. This is a different records group than the Unit Card. Those records MIGHT include a history written by the unit for the War Department, a requirement. That history might include either the ship name or the shipment number.
There is also a web site focusing upon troop movements and lists unit, ship name and dates. I suspect if you google troop movements you will find it.
I'm attaching a worksheet/article I wrote on how to research ships in US records.
It dawns on me that you might want to look into the UK's records since the 505th may have been aboard a British ship if they sailed from England. Their National Archives at Kew is on-line, and sometimes the records are downloadable...for a small fee.