Characteristics of "BowTie" & ZL-1 blocks???

[Hemi_Joel]

Hi Guys, I need to get educated on the Chevy replacement big blocks, and I figured you guys who hang around this place are the experts.

What exactly is a "Bow Tie" block? Does it come in different varieties? Are they all raised deck, and/or raised cam? Do they allow a bigger bore or longer stroke potential than a 454 or 427 block of the muscle car era? WHat are the external differences, how can you tell the difference in a Bow Tie block and a vintage big block by an external visual inspection?

Also, regarding the new replacement ZL-1 block; Are their any improvements over the original that would allow it to have a bigger bore, stroke, improved oiling, better metalurgy, etc.? How can it be identified from the exterior compared to the original?

Thanks, Joel