DBT, I'm not an expert, however I'm an enthusiastic collector. There appear to be two schools of thought on running in an engine - one, expressed here before, is to "drive it like you stole it" from day one. The other, which I firmly believe in is simply this:
No higher revs than 3,500 for the first 200 miles. No higher than 4,500 for the first 500 miles. Don't sit at a constant speed you need frequent gear changing and varying speeds. Don't be in the wrong gear going up hill or pulling away (i.e. so that that the engine won't labour).
Once you're at 500 miles, just go a bit easy over 4,000 rpm. 750 miles and you're nearly there, 1,000 miles and you're engine's perfectly run in (broken in). Some say that it's 1500 miles before it's completely free - but a sensible 1,000 miles of driving and then you can be a lunatic is my thinking!
I've asked pretty much every head technician at garages where I've had cars - from Lamborghini to Aston, Ferrari etc etc. They all say that if you break them in hard (i.e. ignore the advice above) that the engine will be a fraction quicker (not by much and hardly measurable) however it will be noisier (rattles) and ultimately may not be oil tight long-term.
Ask a salesman "oh yeah, they're all bench tested and already broken in - just put your foot down"! Treat it with courtesy and you'll be rewarded. The temptation to mash the throttle is almost overwhelming. Resist it is my advice.
