you can do it 2 ways:
1. Lay a groove in the head and put the Wire in that groove, of which some of that wire sticks out and presses the gasket to the block.
2. You can put the groove and wire on the block, and a "reciever" groove on the heads. This pinches the gasket between the wire and the reciever groove.
The first method will solve the problem, the second is even extra insurance.
the other problems that arise doing this is that the block is way heavy so you will not only be transporting the heads, but the block as well. This is much more expensive because you have double the machine work to be done, plus the math to line up the reciever groove w/ the wire. And most machine shops wont work on parts that are perfectly clean, most require a chemical bath which is expensive and damaging to gaskets.
This is why I personally chose method 1. It worked for many including Darshu, i am confident it will work for me.
Hope that helps