I recently reinstalled my fuel guage and tank sender, both of which I had sent to Nisonger's to have rebuilt and calibrated together. (BTW, I ultimately pulled and reinstalled the sender with the arm facing forward as suggested by several Healey mavens). The fuel level indicated does vary under acceleration, braking, etc. but is fairly constant at constant forces. However, I regard the fuel guage's indicator as nothing more than an interesting diversion to the road ahead and go by my tripometer, which I find to be more reliable and definitive: My gas mileage varies little whether I am driving around town or on the road--about 25 mpg at all times--I'll usually refill at 200 to 225 miles and I see no reason to plumb the depths of my fuel tank.
Best--Michael Oritt, 100 Le Mans