I was going to make a dio of the British Red Devil capture of Pegasus Bridge. However due to the complexities of scratch building a glider and the bridge I have decided to postpone this project to a later date.
Now I want to do a D-Day Sherman but have discovered that there is no suitable kit readily available without serious money for update kits. So my question is this...
What if I build the M4A3 Sherman with wading trunks even though it was introduced for a month after D-Day? As an alternate I could build an M4A1 75mm but with large hatch, which I understand was really only used for DDs. Neither tank would be accuate for D-Day, but then no kit out there would be. Would this glaring inaccuracy be OK for the campaign??

All the references that I've found are for the small hatch M4A1 or for an M4 ( as per Tamiya kit). Steve Zaloga used the DML/Dragon hull for his diorama ( Military Modelling Vol.33 No6 June 2003).
In fairness to all the other entrants that are spending time, money and effort to produce a model that is as accurate as they can get it, I really should say no. However, as I cannot prove that NO large hatch M4A1 were used, and in the spirit of the campaign I will allow the large hatch M4A1, but not the M4A3. My decision is based on the fact that the deep-wading tanks were an important part of the landing force and should therefore be represented in the campaign, and that there are no easily available and affordable kits of the subject vehicle.
Just remember that all the hatches and other opening should be sealed with a buff/dark yellow canvas or with a tape, including fuel fillers, hatches, ventilators, gun muzzles (until the tank was ashore) - some job!

PS - unless of course some kind soul has a spare DML small-hatch hull that they could let Shermie use - it would be a better option!

Dave that was pretty much the answer I expected. I did not feel good about doing it that way. l I think I will just have to break down and get the Tamiya M4 Early.

OK I broke down and bought the Tamiya M4 Early. I am going to model one recently offloaded from an transport immediately after the initial landings. I might be able to get a little bit of the artificial roadway from one of the Mulberries in the scene.

If you can get a piece of Mullbery in the scene it would be fantastic. My Grandfather was a civil engineering draughtsman and did some of the original drawings for them.

Dave, I will try my best to research the road sections of the artificial harbors. Of course, I will not be able to include one of the Mulberry units since they were waaaay offshore. The best I can get is the roadway. Time permitting, may be able to get a huge convoy of vehicles on the roadway offloading from transports! Won't that be awesome?!

Not huge convoy, don't overdo the limits in the rules. Seriously it would be great to see a small section of the roadway. I don't think that I've ever seen it in a model before, so it would be a coup for the campaign as well.