Is the bore different between 318and 360 or just the stroke? If you're having it honed anyway maybe it doesn't matter. Have a 318 block I'll sell you cheap...
318 bore is 3.91" and a 360 is 4.0" so there's .090" difference. Some say an early 318 is capable of being bored out to 4" but I'd never try it unless I had it sonic checked.