299 LHD 365BB's were made, and 88 RHD ones. Of the 88, there were 58 orders from Maranello Concessionaires, so 58 original UK 365BB's.
The biggest problem with Boxers is finding a good one. There are very few out there, and of those few there are only a couple that actually run well. Mine was restored just before I bought it, but it took me a long time to get to be reliable. So what a car is worth is a bit difficult to say, it is quite car dependent. The Boxer market is also difficult, they are underappreciated and misunderstood, more so in the UK than anywhere else IMHO. On a global scale, the 365 is by far the most desired and prices for a good LHD one are significantly higher than 512BB's and 512BBi's. In the UK, however, this does not seem to be the case. When I bought my car, I drove a 512BB and a 512BBi at the same shop on the same day, and the 365 was the least expensive. It was one of the reasons I bought a RHD one, it saved me about GBP40k.
In Europe, a 365BB is currently for sale for €300k. Whilst this is a fantasy asking price, there is slowly getting to be more recognition for these cars. Many people have stated that the car was far better as a driving machine (but not as a touring machine) over a Daytona. If I would be selling a top LHD 365BB, I would be asking €200k. For the UK market, prices are rising but there still seems to be a lot of resistance to pay much more than GBP100k.
My car is for sale, just not yet advertised as I plan to take her to Scotland in early May for a farewell tour. But should anyone be interested, you're welcome to contact me. She will need to go to a good home so she won't be sold to just anyone, and my price will not have a lot of bargaining room. But you will get one of the best Boxers out there, with a great history file going back to Birmingham, 1st July 1974. It is one with desirable specification: it has the non-adjustable seats and the old clamshell of the very first 365BB's, but it has the upgraded gearbox and some other improvements of the second series. And I just love that 8-track radio which is specified on the delivery sheet of the Ferrari factory. If it wasn't RHD, I would never sell it.
As for the driving differences between the Boxers, I wrote an article about that day at Fosker's in 2008, when I drove all three. I then decided to buy the 365BB, which for me was a car that was significantly more fun. The 512BB is a better car, particularly concering the clutch and move to dry sump, but it is less manic. It has more torque, in a flatter curve too, but a longer first gear and a lower rev limit. It has a similar sound to the 365BB up to the 6,000rmp mark but then the 365BB starts screaming much more, giving you that sensation of the 312T of Niki Lauda (also a flat 12 engine). The 365 engine is more rev happy, better on the cam, and people who have owned a 512BB have told me my car is definitely faster. I have not had a chance to test directly against a 512BB - if I do get a chance I will make a video of that, as I know a guy in the Netherlands with a fantastic 512BB. The article I wrote you can find in the freely downloadable magazine FerrariLife Quarterly #10 on FerrariLife.com. But - I also have video of those test drives and I was editing that recently. I will try and get that video up soom and will post the link here.
Once you start knowing these cars better, the styling differences on the 512BB, to my eyes are significant and for the worse. To my eyes, a 512 doesn't look much like a 365BB. The 512 has a much flatter stance, the rear deck lying lower. The 365 has a 'pouncing' stance, giving a more sporty look. The rear deck is shorter, giving cleaner lines, but the 512BB rear deck has also been rounded and softened, which is not an improvement. The move of the exhausts from out to in was also a strange one to me, giving a less aggressive look. The lack of a front spoiler, whilst a negative at speeds over 160mph, makes the car look much better at the front, too. Unlike a lot of 365BB's, my car has the original 215 'balloon' tyres, which for me give just the right 1974 look, especially with the knock-ons. Later, wider and flatter, tyres give better cornering speeds but ruin both the ride and the look, with massive holes in the wheel arches.
For me, as is clear by now, the original is best. Although technically the lesser car, it gives the best driving sensation and sheer feeling of driving a '70ies glam rocketship into the Apocalypse! Having said all that, the 512BB is great, and so is the BBi. They just have different personalities, and you must try which one suits you best.
A couple of examples highlighting the differences in design.
Comparing the rear decks of the 512BB and 365BB (mine with non-original exhaust):
Lack of front spoiler and covered foglights.
Difference in stance. Hard to capture on photos, but note the line on the side of my car dipping down towards the front, compared to the flat stance of the yellow 512BB.