Why does the Samuri cars stir so much emotion here? Are they such an important part of the Z history in the UK?
I'll try to give a few pointers...
They are - arguably - an intrinsic part of the S30-series Z's history in the UK. They were a small, shape-shifting outfit which punched above its weight somewhat, and were widely publicised in-period due to close connections with the UK motoring/motorsport press.
In my opinion there was a kind of 'Holy Trinity' of noteworthy and successful 'Samuri' cars in period. They were:
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FFA 196L' - the 'first' Samuri 240Z, ostensibly a road car which was a rolling test-bed for the company's developments, and which was modified on a rolling basis. This car generated a lot of publicity in the UK, and was also entered into some club races/hillclimbs etc.
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BIG SAM' - this nickname (connected to at least three separate bodyshell identities) was initially given to the second of two ex-Works rally cars that had been turned into race cars by a privateer racer called Rob Grant (see my post further back in this thread) and which had been campaigned in the UK, Europe and Africa by Grant. It then went into the hands of Samuri and slightly modified/painted in Samuri house colours. Notably it was driven by up-and-coming driver Win Percy, who won a UK Modsports championship series in the car(s). After a big crash, another (LHD) ex-Works rally bodyshell was used to rebuild the car. It still exists today, having passed through many hands, and has been progressively modified over the years.
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LAL 909K' - another standard road car which was modified to go racing by Samuri, and which took part (somewhat amazingly) in rounds of the 1977 World Championship Of Makes as a Group 4 car, again driven by Win Percy and journalist Clive Richardson. Another example of Samuri somewhat punching above its weight. The car still exists, and is undergoing restoration in the UK.
There were many other cars modified by the company, but none - in my opinion - as notable as the above three. For UK-based Z owners the 'Samuri' name represented a particular image of Zs that were modified for race and fast road use, easily recognised by their signature house colours and graphics, and widely covered in the specialist press. It's as simple as that in essence.
There has been much wrangling over the company name and who has the IP rights etc - as you can see on this thread - and it has all got quite messy with regard to authentication of original customer cars, 'tribute' cars, later sanctioned builds and all sorts of other shenanigans, but the three above cars are pretty much the stars of the show really.
I wouldn't necessarily expect anyone outside the UK to know all that much about the Samuri story, but there's some interesting history there that does have a place in the Z's wider story. Contrast it to the (never knowingly undersold) BRE and Bob Sharp stories from the USA, which almost every early Z fan will no doubt be aware of, but nonetheless are essentially about local championships with fairly limited participation...