I had a set of NOS 810 heads that took me a while to sell. I wasn't even asking a bunch of money for them, just trying to sell them. They were purchased new from a local dealer in the late 70's and then sat on a shelf for 40 years. Still had the original box and paperwork. I didn't have any use for them.
Couple reasons for that. That is an earlier version that was 'crack-proned' which made it risky to afford the costs to commission. In other pics it shows the ribs as described by Duane. The latest ones even had a useable valvejob!
