opinions please, on how to break in ....

Break in procedures vary about as much as the number of guys who build engines. I'll tell you what I'd do and leave it at that, since I've had no problems doing it.

When the engine is initially fired, do a quick check of the timing and oil pressure, check for leaks, and do a cam break in. Do not use synthetic oil, unless your ring manufacturer spcifies it. Most synthetics can actually inhibit ring seating. Run the engine at 1500-1800 RPM for 10-15 minutes, go to 2500 RPM for 2-5, then slowly back down to idle. Allow 5-7 minutes to cool, then shut it down.

Do a tuneup, set the timing properly, adjust idle mixture and speed. Then, you can quit for the night, or take a drive. Drive the car gently until up to operating temp. This is the time to look for issues of cooling, oil pressure, driveability. Once up to temp, hold a steady speed for one or two miles, then speed up or slow down, but gradually increase the speed. When increasing the speed, do not be afraid to get into it a bit. You want cylinder pressure to act on the rings to seat them. Drive at least 25 miles this way. Take the car home and check for problems. By now, there shouldn't be any.

Let it cool, and then drive it like you own it for a total of 100 miles. Change the oil. Stay with non synthetic for 10,000 miles, then do as you see fit.

Hope this helps.