ball turret didnt work in the 24d properly. and the ventral gun was aimed using mirrors, I believe. I looked at several different sites. they all mention the nose guns as interfering with the bombardier and the ball turret/ventral guns as being useless. there were many, many variations of the b24d, mostly to try to fix the nose/bombardier/ventral gun issues. they never got fixed until 4 two-gun turrets were installed in the b24j.
If you really want the b24d, just pretend the nose/ball turret dont work in the b24j and that will be close to the b24d.
http://www.historyofwar.org/articles/weapons_B-24D.html
semp
Got lots of stuff here on the 24 semp

Go back and re-read the site you posted. It mentions when the Ball turret was added. The B17E had the same remote turret and it to was replaced early in production. The B24D got the ball turret very early in production as well.
As for the guys asking about the colorful paint jobs. Those were formation assembly ships and not combat birds. They'd been retired. It's already been discussed with HTC in the skinning forum and not an option since they are not combat birds.
Tyrannis, there would not be a lot of fun scenarios for the PTO and ETO as the turret nosed 24s were the main birds. The glass nose D model is best known for Ploesti but the turret nosed 24s did the majority of the dirty work