Shouldn't you be able to take a heatsink base and make a few cuts etc. and get a "theoretical" cpu block?
In theory, yes, that's all a water block is...a heat sink block that's drilled for water passage and milled for heat dissipation.
well if it works well with no leaks it could be done with the standard amd cooler saves alot of money
Depends. Are you planning on just running water through the circuit; in one side of pipes, out the other, through the pump, repeat? Or will there be a radiator involved to help dissipate heat? I'm thinking you might want to consider the radiator as well, but by the time you account for parts and items to make this happen, you'd be better off with an actual water block that will perform better. Cost would be the only thing I'd consider being a drawback when attempting this mod...that and the flow restriction from the heatpipes.
Still though, interesting project.