Here are some ads for Yenko's ZL-1 block:
https://www.yenko.net/oldads/yad8.jpg
https://www.yenko.net/oldads/yad9.jpg
https://www.yenko.net/oldads/yad10.jpg
Yenko was also working with Weslake Engineering in the mid '70s to get a set of aluminum, 4-valve per cylinder, hemi-heads for the 302. The ad they had worked up stated "580-600 horsepower: From a 302!" Pretty wicked looking heads (we've got some pictures of these things I will post later).
[Edited by Chevy454 (10-22-2001 at 11:49 AM).]