It insisted that Israel used Merkava 2, 3 & 5s in South Lebanon recently.
Wrong! There is no such thing as a Merkava 5. The Merkava Mk4 is latest development.
Do a web search for Merkava 5, you will get some results. But there is no proof of it's existence. It appears that a Merkava 5 may have been in development, dropped for budget reasons in 2004. But this is not verifiable!
No Merkava 5 has ever been produced, nor is there any available drawings to indicate any development.