I use this piston in cgi block on 8.1=1, Ian Howell supplied them, he may know the spec of piston as he did have some wrc stuff i think.
Tyr his old website area6 or areasix.
Cosworth may also supply you technical drawings for the piston. I know my bike uses cosworth pistons with offset pin with longer pankl rods, and I know Ian did use longer rods in some engines.