I'm sure this has been discussed before but couldn't find in the archives. I've got a Holley 750 on my 440. Works well until I get in stop-n-go traffic. Has a really bad stumble when I start from a dead stop. I'm sure its because of the heat. I've read about different types of spacers that will help the heat from being transferred to the carb and boiling the fuel, but what is the best?

Get the wood spacer. This is the one I got but it depends on your carb.
http://www.summitracing.com/parts/EDL-8722