I'm searching for the design plans for a Custom Pentium 4 waterblock. Rather than take a regular AMD design and put a mounting plate over the top I'm looking for one someone has made for the Pentium 4 mounting holes of casing.
If you browse to the water cooling stickies section you'll find a waterblock gallery. Here is a link. You can look at their designs to get you started. You might also want to go to www.dangerden.com and look at their RBX and TDX blocks. The P4 version has extra material with the mounting holes extending from the sides of the top plate.