Depends which age of Mini and the gauge, I, IIRC, on my last Spridget had four different dual gauges (oil pressure/water temp) one returned as it didn't register the same as the two before and one after and I contacted the "Smiths" manufacturer (carbolt-ish sort of name) in Wales and learnt about their calibration for the water, this was closed ether tube with end bulb type of system not electric sender and gauge type. My coolant needle was well before the 'N' on the gauge for normal running, others owners worried about the needle being on the 'N' and the 'N' 80-somthing C, I always said to look at the combined gauge and if it showed about 5 to 10 passed 7 as a clock that was fine, if mine got to 'N' it meant it was a bit warmer than normal so I set the variable control for the electric fan to keep the needle before 'N'.
D.FYLAKTOS would have a heart attack if he had B V8 with numbers on the dual gauge, oil pressure at idle being so low and water temp when it gets really hot and the needle pushing into the bigger numbers on the oil pressure part of the gauge. A mate had a Rover P5B and at tickover the oil pressure needle barely rose and even clogging along the needle didn't raise itself too much, I can't remember if it changed with the TVR 4l engine, such a heavy car (not compared to todays lardy cars) I can't remember that much difference in performance to the original 3.5 but I only drove it a few times with each engine. I did notice on following him back from the NEC the very small rear tail lights on a grey car out in the dark countryside a reflective rear numberplate would have sorted that but of course black goes with grey (to, too, many).