318 with 340x heads sluggish

I had not heard that milling over .040" from 360 heads would cause warping issues.....can someone comment further on that?

Once you mill about .090" off the open part of the 'open chamber' is gone and you get a much tighter closed chamber. But the stock 318 pistons will still be .080" to .090" 'in the hole' and you still won't have improved CR that much. Rahter than a lot of head work, I would not hesitate to change pistons; there are plenty of choices out there ready to go to that will get the CR right up to a nice 9:1 range. If the engine does not have a lot of miles on it, then you can probably get by with a re-hone and avoid a re-bore.

Once the heads are off, a cam change is easy, and a torque converter change is not that much more work.

BTW, I have been sick with a damned cold and sinus infection....but RRR's first post here made me laugh and I feel all better now! LOL Tnx, RRR