I've always been under the impression that the A6 was not introduced until after Normandy. Of all the books about the Airborne in Normandy I've read, they all will state the A4 as the version used. A lot of sources will positively state that the A6 wasn't issued until Sep' 44 and Holland. That includes memoirs from troopers themselves, some of whom desparately tried to hold on to the A4 during MARKET, as they felt it was the better weapon.
TO&E's are sometimes misleading as changes in written literature weren't always implemented by units on the date/period indicated. Likewise changes that were implemented by units sometimes didn't get updated on the TO&E for months.
In my opinion (not that it counts for much...) the M1919A4 would be the accurate option for this time period.
Gammon grenades are mentioned in dozens of first hand accounts of US and British Paras in Normandy. They may not have knocked out many tanks but they should still be there. (One sources I've got claims that 80% of the German armor knocked out at Arnhem was by the Gammon bomb. They were effective...)
Adam.