It is my understanding a limited number of engines were produced and urban legend say a few pre-production cars were actually made [img]<<GRAEMLIN_URL>>/dunno.gif[/img]
Colvin's book lists the engine for 1971 and I've seen other literature showing the engine as an option that was 'cancelled' very early before any cars were built.
Here are a couple of links that discuss this very topic...
http://www.chevelles.com/forums/45-c...454-425-a.html
https://www.yenko.net/ubbthreads/ubbt...opics/404475/1
Those #026 heads have to be a pretty rare item...
-wilma