Based on your readings, your new sender would just peg the gauge a bit in each direction because it has a greater dynamic range from empty to full than the old one, i.e. at 8 ohms your fuel gauge should read more than full, and you would go to empty a slight bit faster than you did before, but not by much and past empty by a little bit at 75.5 ohms.
When you measure the resistance with the ohm meter, watch how it changes as the arm moves. You may have a problem where the resistance is not linear, i.e. it goes very quickly from 8 ohms up to 60 ohms or more, then only slowly from there. Look for nice, gradual change in resistance, especially from the 8 ohm side. If it isn't gradual, the internal potentiometer that varies the resistance is poor quality and nothing you can do there - it is a poor quality unit.
I don't know enough about these to say that at the 8 ohm minimum it could have put through enough current to hurt your gauge versus 10 ohms minimum of the old sender. Perhaps someone else knows that one but I suspect these old gauges were meant to take large tolerance swings and that is not your problem.
