This cylinder head was part of the nice update done by General Motors of Brazil on the GM250 engine, turning it to the Chevrolet 4.1 MPFI for the Chevrolet Omega back in 1995. Besides this nice iron 12-port head, the engine received a one-piece rear crank seal, 6" rods, lighter/shorter pistons, Bosch Motronic 2.8.1 Sequential Fuel Injection, among other goodies. I still have one of these engines stored in Brazil and I miss it badly…
Should point that this head does not flow all that much (unported), but its redesigned combustion chamber (along with the thickest deck surface) makes it well worth it, specially for sequencial fuel injection straight-sixes…