What I have appears different than yours. But I will describe mine. I bought them in 2002 from Mike LeFevers, then with Shelby. If I don't help you, try to contact Mike at Mitech Racing Engines-he helped design and R & D them.
They have a full C5AE-F in between the center exhaust ports but no sig there. Mine are signed on the left end of each head with 20 S 01 above the sig. There is a raised 'S' cast on the left upper corner which you can just see here.They are cnc'd, 79cc chambers, 2.250 x 1.75 valves and stage 2 cnc ported. They flow 320 and 230 at .600".
Hope this helps.