change the oil and filter, and go run it like you intend to from now on. I try to give them 500 miles before I hold them wide open, but the guys who build race motors have them screaming on the dyno before the paint is dry.
I have been building engines for 20 years and from experience I can tell you that the only break in period necessary is the time it takes to fine tune the new engine and thats it.
As said above, change the oil at 1000 to 1500 miles and drive it!
I just did the 360 swap in my 79 CJ5 and I am really enjoying the power increase!!