I would call Speedy Bill Smith at the museum listed in my prior post, he displays all these special heads, and that one isn't in the museum.
To use it, would cost magnaflux and surfacing expense of $100, and it may give about 3-5 hp boost.....rather heavy iron, the new 6:1 compression 'Z' head is a better deal IMHO.
Tests of heads on this site:
http://clubs.hemmings.com/frameset.cfm?club=MTFCTulsa