You could do either. But I would prefer the 351W, which is what I am planning on using in my 67 Fastback. The Windsor has a better aftermarket and is more plentiful than the Cleveland. If you decide to use the Cleveland, try to find a 2V versus a 4V. The 2V has smaller intake ports in the heads which is good for street use. But if you plan on using aftermarket heads, which are harder to find for the Cleveland, then it wouldn't matter. But as I said before, the Windsor is quite plentiful, I believe they are available from 1969 to 1996 and have a lot more aftermarket parts available. The blocks from 94 to 96 are true roller blocks while the earlier are not. I plan on using a roller block in my car. But they are not easy to find and if the seller knows what they have they won't sell it cheaply. Good luck in your search!