well, spark plug looks good to me. The head looks funny how u can see that little swirl mark. Were u using pump gas? Or 110?
Here's what I would do:
1)Get a brand new precise metal ruler and a set of feeler gauges. Sit at a well lit table or bench and lay that ruler on the head at every angle possible and try sliding in the small feeler gauges to check for warpage.
2) check the piston rings. Particularly the gap between the ring and ring groove.
3) check and make sure wristpin and rod bearings still feel right. I'd just pull up and down to feel for play
4) read the link I sent. You can use that math to figure out your compression ratio. If you are not sure how many cc's the head is, then you can fill it with water then measure the water in a graduated cyl to find out the cc's
5) If the ruler shows the head is warped, don't worry, just have it cleaned up by a machine shop, but tell them to take exactly what you need off (whatever the largest feeler that fit under the ruler was) as long as it's not more than .030. That would leave your squish at .018.
6) decide what compression ratio would best suit you and order the corresponding dome per the formulas in the link I sent. Buy a cometic gasket kit, put a little dab of never seize on your head studs, properly torque the nuts, then retorque after the next few rides.
This is just what I'd do man. I'm not a champion engine builder by any stretch, but I'm no dummy either.