Both a/c flown by the 408th BS were B-26s with spinners: #40-1391,
"Suzie Q", and #40-1424,
"Satan's Playmate"; the a/c flown by the 69th BS were early model B-26B with spinners. I have not been able to locate their IDs, but Collins' plane carried the nickname
"Winsockie". All a/c had .30 caliber guns mounted in nose, waist windows, and camera hatch. The B-26's tail position when open looked like this:
You can see the tops of the upper canopy halves, with the semicircular cutout for the gun in the closed position visible, tucked inside the tail cone. Also visible are the tracks on the rear bulkhead which guided the canopy into the closed position, as well as the latches that secured the canopy in place (left and right, just above the plane of the gun barrel.)
There is a much better photo of the tail position on page 70 of
The Revenge of the Red Raiders, Eagles Over the Pacific, Volume II, IRPC.
There seems to be a lot of confusion about the B-26 and the B-26A. B-26s were flown in action by the 22nd and 28th Groups from 1942 to 43, with refurbished B-26s flying with the 22nd's 19th BS into January, 1944. The B-26A was used only for training by the USAAF, but lend lease Marauder Is were used by the RAF in the Med.
I think some of the confusion has to do with the fact that turret production was severely backlogged and most B-26s prior to the outbreak of war did not have them installed. This was rectified shortly after Pearl Harbor, and all B-26s committed to combat zones had turrets installed.