My toilet is pretty old and scratched up (thanks to no TLC from the previous home owners), and lucky me recently got an almost new one for free. I do want to replace my old one now, but there's a problem. The new one is fashionably low-flow with one of those silly 1.6 gallon tanks which I will NOT use in my house. So, my question is this: are toilet systems created to mix-and-match, i.e., can I put my old tank on the new toilet, or do I have to use the low-flow tank with it? Meaning, is there a difference in the innards of toilets depending on which size tank it's sold with? I'd appreciate any input you might have.