Are there any slimmed down versions of Chrome that don't include Chromecasting or Hangouts or Facebook or etc., etc. I'm looking for a lean 64-bit build of Chrome.
Err, well as far as I've checked my version of Chrome doesn't "include Facebook" and in fact I needed to install an extension to include Hangouts, but if you're looking for a version of Chrome without the proprietary bits and blobs (which presumably includes this, although I could be wrong), you should just use Chromium.
Failing that, as others have pointed out above this function can be disabled.
There are also plenty of Blink and WebKit based browsers out there, although as someone who's quite satisfied with Chrome and Chromium and uses Google services extensively (and so benefits from such integrations) I can't say I've used any extensively myself. The Vivaldi browser seems to be the new trendy one, last I checked, although it isn't as open as Chromium. And if you're looking for a lean 64-bit build of Chrome, even if existing builds aren't lean enough for ya you could probably skip some things at compile time and slim it down even further if you built it yourself.