STOCK HEADS OR ALUMINUM AFTERMARKET ?

I HAVE A PAIR OF B BLOCK HEADS DRIVER # 2843906 PASS. #2843900 (1) ARE THESE A GOOD SET OF HEADS TO HAVE REWORKED ? (2) THERE WERE A COUPLE OTHER #'S ON THE HEADS 04090 & 03060 , ARE THEY EVEN A MATCHED SET ? (3) ITS OBVIOUS THAT THERE WOULD BE A SUBSTANTIAL WEIGHT LOSS , BUT WOULD THERE BE ANY ADDITIONAL GAINS ? CRACK THE BOTTLE & STOMP THE THROTTLE ! ! !