Honda GX390 cylinder head dowel removal

[Fulltilt]

One trick I use is to countersink the headbolt holes a bit. Obviously you need a big countersink, a wood one will work, or use a large drill bit by hand.
Also not a bad idea, to check the cyl. bolt holes for chamfering, or slight raising. If needed, you can usually do a decent job of trueing up the cylinder using a large ( the bigger the better) thick, single cut mill file. Obviously you want to stuff a rag or paper towel in the cylinder.
As for the head gasket, all the ones I've dealt with were the composite type with the metal fire ring. Don't ever recall running into a solid shim type on a Honda.