You'll get as many opinions on break in as you will asking what's the best oil/filter to run. Assuming your machining/clearances and assembly are all top notch, I would simply check for leaks, gauge readings and unusual noises upon first start up (be sure to prime the oil system before first start up). Assuming all goes well there, I'd put 25-50 miles on it during two or three different heat cycles - I'd probably check torque on the lower intake and header bolts after the first couple of heat cycles. Then I'd change the oil and filter to get rid of assembly debris -- and feel free to drive it any way you want after that.
