I've got to get obsessive here

[broon]

If you can, don't cut the whole top off. I did that with one of my 16 gallon kegs and it won't support a 10 gallon boil. If you can, cut a hole in the top. That way you can still use the handles to move it and you have the full capacity of the keg to boil in.

[jayhawk]

Excellent comment. I still have the handles on my converted keg and they are essential. Keep em there.