The MGB electrical system was designed by someone who had never been inconvenienced by an electrical fire. The positive-ground system on early cars is just the beginning. By the mid-sixties they flipped to negative ground but kept the Lucas component philosophy, which is that anything important should be protected by a fuse rated approximately ten times higher than what the circuit actually needs.

The fix is methodical: get a wiring diagram, trace every circuit, replace the fuse block with a modern blade-type unit, and eliminate every crimp splice you find. Solder and heat-shrink everything. Forty-year-old wire insulation crumbles when you look at it wrong.

Budget a week for the rewire and you'll have a reliable car for the next decade.