If everything is in pieces then I would start with the radiator core support, followed by the inner fenders, the the outer fenders. Leave all the bolts a bit loose until everything is properly aligned. For the bolts going into the fender well I would suggest coating the threads with small dab of anti-sieze if this is your final assembly. This will make it easier on the next person who has to un-bolt the fenders. Go slow and have some help with you.