A couple of things to note here: Splayed, billet-steel, 4-bolt mains are an upgrade from the original ZL-1. Also check out the engraved cap. The enthusiastic staff at Schwartz Machine in Warren, MI, who finish each raw casting for GM, began etching each main cap with the "ZL-1" logo. GM didn't ask them do it-they just did it because they understand the history behind the block. They engrave the rear cam plug, too.
The pair found the tooling gathering dust in a corner of the foundry. It hadn't been used since the '70s. Though dusty, it was in excellent condition. In fact, with an estimated 300 blocks poured altogether, it was almost new compared to tooling used to make blocks by the thousands.
Arrangements were quickly made to have the ZL-1 tooling shipped to the foundry that makes current, aluminum GM Racing small-blocks and heads. During the next couple of years, the ZL-1 tooling was cleaned and revamped. Improvements were made on a few of the block's design details before pouring the first "new" ZL-1 block.
The biggest improvements included screw-in, O-ringed water jacket plugs and splayed, four-bolt 8620-billet steel main caps. The lifter valley was also modified to accept Gen VI-type roller lifters.
Overall, quality and serviceability of the block were improved. This better version of the ZL-1 offers brand-new blocks from the tooling of the originals. The best of both worlds, wouldn't you say?
No, the best would be some sort of ZL-1 crate engine. But it's not available... Well, not yet anyway.
Oh, wait. We weren't supposed to mention that!