W2's

Good mention on the adapter plates. TTI makes headers with ether bolt spacing for what ever head you have.
The offset rockers are available. But as anything off set, it can be a little pricey depending on manufacturer.

TD & Jesel are pricey but worth it if you’re racing.
Harlan sharp is a fine rocker for the street.
Adjusting the rocker shaft system for proper height and geometry always has been a PIA.

I’ve seen pictures of these oval port heads ported into huge rectangle and squares. That is the maximum effort port with no care or consideration to any rpm under 5K or better.