I know one thing that is fact,,,, the eddies would be lighter.
If the J heads was just stock I would say go with the eddies with no problem but the J heads have been ported so that upped the flow. Have you seen the heads? Have they ever been flowed? If so what are the flow numbers? These are the type questions I would be asking the builder before I spent $1200 on eddie heads. Heck they might out flow the eddies.