You can lap down a piece of C110 flat bar to make a cold plate if you would like. You can find it on eBay pretty cheap at times, just be sure to get C110, or some rate it as "Class 1", it's almost pure and has good thermal transfer, easier to work also.
Flat bar will usually have a little cup on one side and it's a little convex on the other, I just file that down a little with a smooth mill file before I start lapping, to save some time. If you have a piece of plate glass to lap on it will come out a lot smoother then if you use plain window glass.
It's easier to just buy one already made but it's really no big deal to make your own.
This one is 1/2" copper plate and it's made to be a integrated cold plate, it bolts to my block, you'll probably just want to use a loose 1/4" cold plate if you don't have a metal block. Thicker cold plates will help a little bit with temp swings, but it will cost you a couple of C to. More pic's here...+++Stinger V-8 Pelt Block
Edited by ira-k - 10/29/09 at 1:52pm