In the late 80's my brother and I ran a very hot little Mini Clubman (not to be mistaken with the present estate-type Clubman).
Is your "new" Mini an original, or one from the late 90's re-release? I can't tell you much about the latter, but here's my experiences from a '70 model summarised:
- The Haynes Manual is actually worth your while.
- Both my brother and I are 6'2" plus, so the first mod was to move the seat mounting points further back so that we could actually get into and drive the car.
- The mechanical fuel pump sits on the back of the engine, right under the exhaust manifold, and is prone to failure whenever the exhaust manifold is waaaay to hot to touch.
- If you think the SU carburettor is Satan's own handiwork then try our approach of fitting twin SU's to have this fact absolutely confirmed.
- When not working on SU carbs Satan was hard at work designing the "hydrolastic" suspension system.
- Oil changes are a mess given the bright idea someone had of putting the oil filter facing downward on the upper front part of the block. Any oil change comes with a mandatory garage floor and engine clean.
- The cooling fan pumps air from the engine compartment out, and not into it like other cars. (I'd rather not tell you how I know this!)
Not much of a problem when in the US, but having to work with non metric fasteners was a major PITA
If you have an early model, there's few things you must consider!
- Get you wife to unreservedly hand it over to you.
- Lose the hydrolastic suspension.
- Disk brake conversion.
- Weber Sidedrafts.
- Free flow exhaust.
- Uprated radiator and bigger fan. I can't quite remember but I thing the 1100 fan had more blades than the 1275 fan, and this helped cool things down considerably.
- If a it is 1275, consider an 1100 crank, 1275 pistons and an agressive 4mm-odd skimming of the block.
- 800cc head with a crossflow conversion.
Above all - have fun!