Would anyone like to trade heads?
1Wilds' suggestion makes sense - Just how much you mill off depends on your intial static compression and what you want to achieve.
Up side with milling is:
- Cost
- retain existing combo ( no need for new rockers, valve covers etc)
- simple process
- take advantage of intake off and port match
Downside is:
- Unported J's probably don't flow quite as well as Magnums.
- Intake will probably need milling dependig on how much you skim off
- You may need to run adjustable rocker gear.
Others may chime in with more.....