This spring I was going to try and freshen up the heads on the 318 in my dad's '57 pickup. The plan was to get a spare set of heads and have them gone through so the truck's engine wouldn't have to lay open for a week while I wait for the machinist to get done. A friend, who has a pile of 318's laying around, said I could pull a set of heads and have them. I pulled a set and dropped them off only to get a call from the machinist saying that the heads I left with him, which were in beautiful shape (his words), are 273 heads. I have never heard of a 273. He said he's never come across a 273 either. He also told me that these heads will not work on my dad's 318. Is there a way to make them work or am I back to square one?