Nothing wrong with using a flathead as I had many in my early cars. But what Bob says is so true. Get the block Magnaflux. I didn't on my first flattie and after putting in alot of time and money I started it up and found the block was cracked. It was carcked so bad that the water would work its way pass the jackets and sit on the piston. If your going to bore it, keep it down to no larger than .040 over. Good luck in finding a good block.