Doug,
427 cubic inch. I bought the block from Joe Fontana. It was from his last production run before he sold the business to Shelby. They (Shelby) modified the Clevor tooling to remove all the 351C parts and replace them with 351W parts. Now it's just an "Or"!
I think Borla's cleaned-up their act and now their TB's are OK. Unfortunately, you're still on your own with them because their tech support is terrible. Also, if you need parts or an ECU they can't supply, you'll be referred to the dealer that buys the most stuff from them, not the one best suited to help you out.
Jenvey Dynamics in the UK makes great stuff but their IDA style TB's only go up to 50mm, which may not be large enough for a "built" Cleveland.