Pete,
I probably should not comment your work too much, as my own 5-ton truck is currently displayed in Rivet Review Board (which is, by the way, more suitable forum for this thread as well, I think). I like the way you converted your model to a different variant and like your improvements on the shelter.

But I can suggest one correction to this model. Of course there are hundreds of minor details that can be corrected in Italeri kit, but one is relatively easy to fix and is quite noticeable. Judging from the wheels you used (with CTIS), your truck is...

...M928A2. And A2 variants of the M939 series trucks have different fuel tank installed than A0 and A1 variants. Italeri model includes the A0/A1 type tank, so it is actually correct for both their M923A1 and M925 kits, but not for the A2 conversions. You can see the shape of the A2 style tank on this photo in Armorama Gallery:
https://armorama.kitmaker.net/modules.php?set_albumName=albup71&id=adj&op=modload&name=gallery&file=index&include=view_photo.phpReal Model resin update set includes the correct fuel tank for A2 truck. Similar part is also added to the OOP Ordnance Models wheel set for M939A2 trucks. I have both these sets and as built my truck as A1 variant, I have two spare resin A2 style fuel tanks and if you wish I can send you one.
And speaking of Real Models - the mentioned set was of rather poor quality and I cannot really recommend it... Here is my review of this set:
http://www.vodnik.net/index_rv.htmThere is also one other external detail in the Italeri model that is not correct for the A2 truck and this time it is a bit more diffcult to correct, as it requires some scratchbuilding, but is also less noticeable. The spare wheel carrier is A0 truck type - Italeri included this same part in their M923A1 Bigfoot kit and it was not right for this version. And this part is also not correct for the A2 truck you build. You can see the comparison of different styles of spare wheel carriers in my review of Italeri M923A1 kit here:
http://www.vodnik.net/index_rv.htm.
Your model looks very promising, even if you decide to ignore those small imperfections I mentioned. Keep up the good work and show us some more photos of your model later!
UPDATE: I just noticed another quite noticeable Italeri error you missed to correct in your model. The floor of the cargo bed should be steel plates, not wood as Italeri (and obiously Real Models also) made it. Just put a piece of styrene sheet on it and it will be fixed

But wait... I have not actually seen the floor of the long M927/M928 truck bed. Still - I doubt the floor would be wooden in this one - it is probably steel sheet, just lke in short bed variants.
Regards,
Pawel