Engine dilema.. 318 or 360?

I would actually go for a 383 or bigger or just keep the 318. If you're going to do all that work it'll be that much more rewarding with a 383. I have a pretty fast 318 in my dart and I know a 360 would be an improvement. But to pull out the 318 and replace it is a lot of work so I'd want to go as big as possible.