Yeah - those were the two I was thinking of. (of which I was thinking?)
It's okay to end a sentence with a preposition. Don't let anyone tell you otherwise.
It's also perfectly okay to split an infinitive.
A lot of the grammar rules we know that go against the way we actually use the English language -- don't end sentences with prepositions, don't split infinitives -- aren't natural. They're 19th-century creations that were designed 1) to force English to be more regulated like a Romance language and 2) to separate the educated from the uneducated. In short, some of these unnatural grammar rules are linguistic snobbery.
For more on the prepositions "rule," check out Lexicon Valley