So I took some measurements; with 2.5mm milled off the head and using flat top pistons the most aggressive cam you can run is a GX spec camshaft.

I've since valve notched the forged JE pistons I have by 2.5 mm. I will be using the standard method of putting clay on top of the pistons to see which camshafts will still be safe to run. I have one that's 278 duration with .420 valve lift (this is what I was using) and the other is 286 duration with .460 lift. I will be trying those tomorrow, if I don't get it done then it will have to wait a few days as it may be as hot as 110 degrees on Wednesday and Thursday.