What block?

The 68-69 blocks are stronger, but they are not roller cam compatible. You would need a roller cam conversion kit (read $$$) to make it work.
You could go with an aftermarket block if money is no object, ford never made anything stock as strong as a Dart block.

If you are going to build from scratch, you should go with an aftermatket block. Dart or World Products. Both will hold the hp.

If you aren't going to really push the motor too hard (ie. no power adders) stock is fine. But . . that's no fun.:winks