ames14 has it correct. The tanks are NOT compatible with each other. I've talked to both Keystone and the manufacturers of both tanks and they cannot to exchanged. The newer molded tank will not fit where the tanks of two part construction are on the older units. Montana Man is correct in that the tank you found Dave is the two part tank (pretty sneaky of them to put the tank upside down in their photo) and it is as they said chemically welded as those in the 2014 and before units are. I've blown several tanks and the main reason most blow or separate is because they have been overfilled OR we have tried to drive down the road with them partway full. The sloshing and splashing or movement within the tank breaks the weld and age has a lot to do with it also. About the only thing those of us can do that have a 2014 unit or older is install some added support under the tanks and also use some foam insulation between the extra support and the tank so it does not rub through the tank. There are numerous posts here on the Forum showing pictures of how some have added this support and foam and if you go into the Search Engine you can find the posts and pictures. DAVE, I'll say one thing for you, you have more guts than I do when it came to removing that black tank.
Good luck and safe travels and camping!