I am pretty sure you can safely go to 427 on the stock block. I am not sure about what power level, but there are a few guys on the site that have gone 427. You can get the 427 stroker kit from texas speed!
217/228 .565 cam, th400 swap with 3600 stall, headers.
Vararam intake, GPI tune, new PB soon
Bring on the Bolton 5.0s please!