I have some Dual Plug Hemi Aluminium Heads Part # P3690038 Casting # 3614433 & I want to fit some Milodon # 27500 Spark Plug Tube Seals. I have heard that these seals have to be individually modified to fit each plug hole but I'm wondering if I can machine the heads rather than the seal inserts so the inserts fit without any modification at all. Is there enough alloy in these heads to machine them the minimum amount to fit the seal inserts without cutting into or getting too close to the water jackets.

Thanks