Miniman you crack me up!
I just thought I'd jump in and add some fuel to the fire...
I have been lucky enough to see my Lillee go through several changes to power output as well as a change in engine capacity. When I had the 1152 I ran it with a single 1 1/4SU and std head with probably an output of something like 35hp atw. I then upgraded the head to one of Graham's sexy 295 ported jobs and dellorto total output around 43-45hp atw.
Both times the car was on a 4 synchro box. When it was runnig a single 1 1/4SU it was a struggle to run at highway speeds. It seemed like the engine was about to throw out pistons at 4100rpm/100km. Not to mention going up hills!
With the dellorto and ported head, she breathed a whole lot better and comfortably revved to 4100/100km/h. It seemed like she wanted to rev harder over that, but of course you feel very uncomfortable sitting at 4100 or 4400rpm as the engine seems like it is screaming it's head off. But after 2.5 years the 1152 was still going stron with no major faults at all.
Nowadays I've graduated to 119.7hp at the crank running on a freshly rebuild remote box. Firstly, there is nothing under 2500rpm except spluttering so to run at such low rpms is probably not good for the engine let alone saving it from wear. The new engine really "wants to rev" and this can simply be described as "when it hits 2500, it takes all of about 3 secs to get to 6000rpm in any gear"
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When running on the freeway in 4th, anything under 2700rpm is almost accedemic for this engine. There's nothing there, it's very sluggish and due to mainly the cam, vibration, splutting you name it. It runs much healthier at 3500 or above and cruises at 4000rpm. It's a much more relaxed feeling at 4000rpm than it was in the 1152 as it doesn't feel like it's even trying.
Both cases I ran a 3.44 diff and I am very happy with it. I think 3.44 is the right diff for a mini with high output as it is a good cruisy high speed diff and gives you good acceleration at the same time.
So my point to all this is that if you are outputting a fair bit of grunt and the engine is well built, it makes very little difference on the highway (which is why we are all talking about a 5spd box/overdrive anyway right?).
Admit I don't do many freeway miles but I would definately not trade in the accelleration for a few more 100rpms on the freeway. The expectation for this engine to last somewhere aroung 50,000 miles before needing attention so divide this by the miles I do a year and it should last me 8-10 years!
I don't suspect that a slightly lower revving engine (say 3800rpm/100kmh) will last a significantly longer time than mine.
Can you imagine 10 years of sluggish take offs??
that`s how long ago it was--> probly like 28 (ish) years ago,,, whew i`m getting old now,,, catching up to the good Doc 
