I think all of the parts stores carry "universal" cylinder head dowel pins. Felpro makes a bunch of them. You just have to find the right diameter.
Just using part of a head bolt as an alignment dowel might not be sufficient. I notice that when I set the head on one of my spare VR blocks without dowel pins and start all of the bolts, the head will still scoot and slide around a fair bit. With dowel pins, its locked solid and won't slide around at all.