Ahh, now I feel dumb, I should have paid more attention to all the reviews and pictures. What I had been thinking was the L7 barrel in the IDF kit is actually the “20pdr Type B” barrel with a fume extractor - clearly shown in Terry Ashley’s review, and that is why it looked weird compared to regular L7s (my kit is not the first edition with both barrels apparently). Now, I think I will build one with the Type B barrel and the other with the L7. For the proper L7 barrel again, would it have the accordion cover (?) at the mantlet or would it be completely “naked”? It looks like the canvas mantlet cover might be covering up the accordion part in the pictures (which, of course, this kit does not include). But, at least, I think I can use the M60 or Leopard extra L7 barrels with minimal change (depending on the accordion part).
In regards to the L7 gun update happening at the same time as the the rear deck/fuel changes, I have read your previous comments here and in other forums. Older sources I found mention 2 major upgrades only, such as Vasko Barbic’s article. The first one is the gun upgrade as mentioned (I am just linking to the images in the original posts) here, followed by the second phase concentrating on the new engine, and the deck and the fuel tank extension.
And then there is the newer sources, like this build that specifically talks about the L7 upgrade with the Meteor engine with photos and the extended rear deck: 1/16 RC IDF Late Sho't Meteor Centurion with 105mm - build - RC Tank Warfare community hobby forum. The various factory pictures I found are also interesting, showing the entire engine deck empty (prepared for the new engine) as well as turrets with and without L7 guns, so I don’t know if there was a distinct phase 1 and a distinct phase 2. As a result, it is a bit confusing if they would have extended the rear deck and added extra fuel tanks without also adding the new engine as upgrade #1.5 in between.
However, I am going to go with the extended deck in the L7 version. For scratch-building this; I think it would be the same idea as the Sho’t Kal parts L46 and L36 in step 5 here: https://www.scalemates.com/products/img/3/2/1/269321-52-instructions.pdf. The Babic diagrams also have the engine extension looking about the same.
For the additional front armor, I think you mean part F8 in the 5/1 options from the instructions on Step 17, which is the only mention of the 5/1 I could find in that kit: https://www.scalemates.com/products/img/2/1/7/100217-14-instructions.pdf. I also thought that extra frontal armor was an IDF addition, not a factory modification for the 5/1s. The kit part also looks different from the Barbic diagrams (#18 here): https://forums.kitmaker.net/uploads/default/original/3X/f/e/fefd2cbbab31e0c5fac09463450671de81eda5d8.jpeg, as well as the Australian Mk5/1 kit’s front glacis part.
In any case, I think making an early IDF version out of the British Mk5 version is not going to be that difficult, considering people used to build Sho’t Kal’s out of Tamiya’s Mk3 kit 
Deniz
