I can't remember where I read it, but I'm sure I've seen somewhere that leaded fuel was brought in later in the war specifically for tank engines, and most vehicles would run unleaded.
The one at the front is an early CMP. The one at the back has a Guy Ant look about it but looks a longer wheelbase than I'd have expected for one. It may be a late CMP but it doesn't look quite right to me.
Just stumbled on this wikipedia article on the Schofield tank. The photo shows the same type of suspension (I think)
http://en.wikipedia.org/wiki/Schofield_tank
It looks like you can see a little bit of lump at the base of the barrel. If so that probably rules out the straight M10. The barrel doesn't look too tapered at the base, so my money's on Achilles. That would tie in with the name as well.
Welcome along by the way
The smaller one seems quite hard to come by.
I'm guessing that the change to the middle one was to be the same thickness as a jerry can for stacking but I've not had one to compare. IIRC the one on the left is the right size to fit two in place of a POW can in vehicle racks.
I'm sorry to say that I wouldn't hold out much hope. I had a similar query with regard to a program on a different channel and didn't get very far. I suspect TV companies get a lot of queries.
Nice truck
For those that couldn't see this is the first URL that was pasted in
http://s914.photobucket.com/user/Clint328/media/Fordson%20Thames%20ET6/20140704_143419_zps83601ff0.jpg.html