I agree with Mark that pistons are a good way to go, what I stated was the easiest. That's what you asked for. To me though having a flatter piston and getting the compression I want is better. Nothing getting in the way of the flame front and angle milling rolls the valve angle.
I don't know what is in your engine regarding " selling what you have and building a high compression motor". The parts in the bottom you have now may be fine.
This is not an attack on Mark's comments. He could be right, I just don't know specifically what you have in your engine. Just my opinion on what you are wanting to do.
Again, is this on gas?
Curtis