Squish Compression Question

You could shave off .020" and that would bring the piston at tdc .028" squish... not sure on the compression you'd have after that, or if the piston valve pockets are deep enough for those cams. All of this will also retard both cams as well.

Can you just use a thinner base gasket?

The side skirt coating is no big deal, and it being slightly worn off does not mean the piston needs to be replaced.

The 13.5 CP may change the squish if it uses a slightly relocated wrist pin. I however do not know the details on it.

Do you mean i will have to adjust the cam timing if i shave the jug??? I don't know about the thinner base gasket...max power told me that they made my jug a little taller than normal so it should be shaved if i want to raise my comp.

If you have a tall jug then you can have it shaved to the spec you want to arrive at. That taller jug would have advanced the timing, and so shaving it will retard the timing back to stock... or close to it. No worries. It's not going to make the piston hit the valves or anything.