Well one second here if you have a 283 bored .125 over you would have a 4" bore right? because the stock bore is 3.875, so you would have a 302? Well I have the 283 block and it would be a lot easier to just bore mine out, but can i bore mine out that far??? The casting # is 3834812....283...1962-63...2 bolt main the ID # is FO72IDK