Hi Slarti,
The wheels are BMW Mini steels. They are available very cheaply (£25 for four wheels and good Michelin tyres) as so money people swap them for alloys. They are 4 x 100 PCD.
The conversion was achieved by buying some nice aircraft-ali adaptors from the US.
They are beautiful, but they were not cheap. By the time I had paid the taxes due I was the wrong side of £200.
As soon as I fitted them I knew they were worth it. Before fitting I changed the standard Herald lugs for the larger MG / Land Rover lugs. They did need to be trimmed so as not to sit proud of the adaptor.
I have just had a look and they now appear to be available this side of the Atlantic -
http://www.ebay.co.uk/itm/Triumph-Cu...SCtMpMjDZc0oVQ
My decision to go this route was inspired by this pic of an MG record breaker -
and I am quite pleased with my eventual take -
By complete good fortune, the resulting track matches the Sammio body perfectly.