I was 8 thousandths off on my 235. Thinking it was only the head that was warped, I took that off and had a machinist surface that down straight, which improved my compression ratio to about 9.4:1. However, my leakage problems were worse than ever. It turns out my block is warped too.
So yes, a head and block can both be warped. I know if I rebuilt the 235, I could have the block resurfaced to match the head, but I'm not sure if I'd still be at a compression ratio that you can run pump gas on. If I jumped up 1.4 points in compression just getting the head flat, It's gonna be even more once the block is planed flat too.
Plus why do all that work for an engine that would be lucky to exceed 140 miserable horsepower? That's why it's a V8 for me.