The stock valves are the same size as the Pontiac 389, 1.92" intake and 1.60" exhaust, but the ones pictured are probably 1.94" intake with the 1.60" exhaust. I don't recall off hand what it flowed, I just remember that it picked up a ton of flow by unshrouding the intake valve.
Here is a picture of the un-ported chamber and valve size. Both these pictures are from the engine I'm putting together, basically cleaned up the parts (hot tanked the head and checked for cracks)
And unported ports.
Rebuilding an OHC Pontiac 250 with EFI and a Turbo