For what it's worth, below is a copy of my project notebook comparing the resistances I measured from the Bugeye fuel gauge to the MGA. I don't remember how I determined that the sender resistance was 0 to 90 ohms; probably measured 90 ohms when the tank was full and assumed it would be zero, like the MGA, when empty. So, take it with a grain of salt.
If you use resistors to cal the gauge, remember a couple things. First, you should get 1-watt resistors, because that's about how much power will be dissipated in them. Half watt (and smaller) are easier to find, but might get stunningly hot or even burn out. Second, resistors are available only in standard values. Some 'standard' values are not commonly encountered, though. So, assuming that the sender is linear (a BIG assumption), you want the closest standard values to 22.5, 45, and 67.5 ohms. These are 22, 47, and 68 ohms, and should be available at Radio Shack. Again, check the resistance of your sending unit to be sure I'm right on the 0-90 number.
I do wonder why LBCs all seem to use this funny arrangement of three coils instead of a simple, one-coil meter movement for the fuel gauge. I suspect it is some clever way to make it less sensitive to the system voltage, which, as we know, varies a lot. But it can't be perfect, since later cars have that profoundly bizarre bimetallic voltage stabilizer, which, I suspect, works about as well as high-heeled sneakers.