Grounding both heads will help with electrolysis when it's running, you have a basic battery exchanging ions through the coolant due to the dissimilar metals in the heads and block. Adding an easier "path" for the electrons flow will help reduce the electrolysis effect on the head studs,head gasket fire rings etc and technically,you get a better spark. I run an earth from the batteries in the trunk to the block, the starter motor turns the engine over a lot easier. Sure it adds weight but your ignition system will thank you.
EDIT: Some coolants also have corrosion inhibitors which will help also but not all drag strips like you to run anti freeze / summer coolant