Really inspect the whole thing thoroughly. Look to see if you see glazing in the cylinder walls or any silver streaking, both very common in a motor that ate coolant. You will have to hone the cylinders if that is the case. Also, get the motor out and tipped forward to make sure there is no coolant in the bottom end. You can TRY dumping some fuel down the holes where the crank is and use it to flush any coolant/fuel goo out. Ultimately there is still no garuntee. I just sourced a good O ring kit from ATV galaxy on the last build I just did for a buddy. When you install it all. Don't try to assemble the whole head and just slide it on. You will decimate those little o rings on each stud.
Best way, is to ring up the domes, set them on with the notch facing forward. Then the main shell. Now drop the little o rings on each stud. Top plate is last, don't forget the two thin rings over the spark plugs.
Viola! Pro Design Sammich!