Eh, I degress...400 blocks are actially more sought after in my opinion for performance engine's. The main saddle's are thicker, the cylinder wall's are thicker, and the smaller journal's are far better for oiling. And, sorry...I meant correct dated block. But, ya ultimately it's only worth as much as someone's willing to pay for it. If you're lucky, you have SR (Service Replacement) blocks. =)