the headgasket looks good. Is that a metal exhaust gasket? i think the hole is too small, personally.
Check out the Porting threads by Maniac57, hit the search. Maniac57 porting
theres 3-4 threads. all good stuff!! i followed them on my latest engine, it rips!!
also ensure that when you mount it, that its 110% solid. these flex and rattle left right and center. if they arent TOTALLY solid mount, you WILL break mount bolts, loose a chain, and/or loose ur rear spokes