Anders it looks as if you bought a 307 car right??? The question you need to ask yourself is "What are you planning to do with it?" Are you going to Pro Tour, Street/Strip, or go back to original??? If you go back to original I would go with GM if you can find it, but if you were leaning towards one of the other two, I would Goodmark it and save some money for a bad ass motor...
..Either way good luck and contact me if you need anything. Mark