They are commonly replaced with aluminum heads, plus the blocks crack while the heads rarely do... I just bought a set cause I wanted a set that had never been resurfaced- and one of them was cracked! I paid $50, plus shipping... Karl
Pound for pound those heads have to be some of the biggest bargains in flathead-dumb. My '47 car is running OK with an external cracked head and have been buying replacements. As usual I have more than ever needed. Started at $15 for some nice candidates but when I really didn't need more they started showing up for less, down to $5. Now I just walk by and don't ask. They must not be very appealing for other performance applications. When I replace the cracked head I would like to have them milled .050" or more to pump up the compression a bit. Won't hurt to have a few candidate heads for that. Good Luck: Fred A