Seeing as today marks another D-Day anniversary I thought I'd get these two together and start a topic on them.

The Heller 1/72 will be built straight out of the box with a small bit of weathering and will end up on a small diorama base that still needs some thought as to what it will look like. Right now all I know is it will get one or more hedgehog tank barriers.

Bigger brother started out as only a cheaply acquired upper hull in which I saw a fun mashup of aftermarket sets and a scratchbuilt lower hull that doesn't need a whole lot of attention since the rear doors will be entirely covered by the rear wading stack. Refreshingly simple and will hopefully build up a lot quicker than the mega M4A3E4 project that still needs a lot of thought in the smallest details. Still undecided if it will also get a diorama or not.

Composite hull M4 was a rare bird in US Army service in Europe (the Chrysler tanks that were accepted by the Army mostly happened to go to battalions bound for the Philippines). However, there were a few in the ETO, notably with 6th Armored Division. However, that division didn't go into action until Third Army was activated for Operation Cobra.
The UK received a lot of them, but most were converted to Firefly (though a few 75 mm gun tanks do show up in UK Regiments).
Most composite hulls had late, low-bustle turrets, with cast-in thickened armor on the right front, and no loader's hatch or pistol port. A few got the late, high-bustle turret with pistol port and loader's hatch--some were rebuilt as Fireflies, and did not receive the British pattern loader's hatch, as it was not needed.

That would explain why the search for references has so far not really gotten me anywhere. Kind of typical for me though because of my love for rare and difficult to obtain things. Your post confirms my findings about the turret, cast-in armor and some getting the later turret WITH loader's hatch is new to me.

Only found one picture so far of a Hybrid M4 in a D-Day book that depicts T263275 of the 1st Northampton Yeomanry dated August 7th 1944, doesn't say if they used wading stacks or not.

Question now is were any of these US designed wading sets delivered to the British along with the M4 hybrids and can anyone confirm with certainty wether any of their US Composite counterparts with this set took part in the Normandy landings?

If not my build will just have to be of a south-east Asian D-Day setting, in which case I'll need to know which units operated them and if there are any pictures from multiple sides as decals will likely have to be custom ordered.

Pacific Units that operated them included the 706th, 763rd, 775th and 44th Tank Battalions. The 713th Battalion tanks were converted to flamethrowers. The 75 mm gun was cut in two, and the outer portion of the tube clamped in place. A US Navy flamethrower was installed in the turret to fire through the non-functional gun tube. Oddly, this highly effective conversion was never done in the ETO.
There are plenty of photos in books and online. Squadron's original "Sherman in Action" (from the 1970's) had a nice selection, and Steve Zaloga's "Tank Battles of the Pacific War 1941-1945" (published by Concord) does, too.

The flamethrower mod you mention sounds a lot like the M4A3 POA-CWS-H5? It seems a few of the M4 Hybrids were also running around in Italy, wondering if they had the stacka when coming ashore.

Same research facility in Hawaii developed both flame tanks. The M4A3 POA-CWS-H5 used an M4A3 howitzer tank with a separate flame tube mounted in the telescope opening in the mantlet (the tank gunner could use the periscopic sight). The howitzer remained fully operable. They were built for the Marines rather than the Army, and missed the war in the Pacific, finally seeing combat in Korea five years later.
I'm sure you'll find random M4 composite hull Shermans in small numbers in multiple theaters, as the Army did not distinguish between them and any other M4. Even if a unit had a batch of vehicles drawn from a single factory, replacements could be from any production plant.
These distinctions only concern crazed hobbyists like us seven decades later.

Got a couple more parts in. Not really knowing which design variant was used I figured what the heck and bought both E8543 transmission housing variants, the one that ends up not being used will then be incorporated either in a different build or will become a standalone on a trolley.