Only the inlet cam of the KR engine is different to the 2 litre engine, I'm assuming you've got the 9A engine, The 2 litre inlet cam was milder because it was mainly for the american market and the cars had catalysts and more stringent emissions. The exhaust cam is the same on both engines. You can fit sports cams to your engine and theres loads available.
As for zeroing the clocks, it is possible and you'll have to strip down the speedo to get to the rotating numbers, use a very small electricans screwdriver and just spin the numbers round to what you want using the little pegs that stick out on the side. Although not to sure on the legal side of it, especially if the previous owners have been filling out the mileage part of the log book when its been sent back. might show up dodgy on a HPI check when you come to sell it.
