As above. To my experience, there aren't any tanks that have reliable survivability. You can tilt the odds in your favor of being able to take a hit, but you cannot guarantee anything. The best thing you can do is estimate how many rounds you plan to fire on a map, and take that many. I've seen a lot of people take a full ammunition load and had slim to no chance of being able to take a single penetrating hit.
"The best guaranteed survivability is simply not getting shot at" aside... If you know you're going to take a hit, and it's probably/certainly going to penetrate, try to put as much as you can between where the shot is coming from, and where your crew is. For things like this (circumstantially) I would say vehicles like the STRV 103, Merkava's, and "tanks driven in reverse" like the IS-2's and TOG have better-but-not-perfect survivability. There are quite a few US tanks that seem to have a large transmission in the front of the hull that can soak up a lot of hits-...
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