Hi All,
While you are installing in-line fuses, I suggest you make a list containing the circuit/component covered, the fuse amperage and, most important, the location of the fuse. Also, I strongly recommend that you also carry an updated copy of your fuse directory in the glove box along with 1 or 2 spare fuses of each amperage installed.
The beauty of in-line fuses is that they are installed into the covered circuit and, therefore, can be located anywhere. I have used in-line fuses extensively in my BJ8 to cover every critical circuit and key component...including my sound system. Although I have not had an issue causing a fuse to blow, I have pulled a fuse to deactivate/separate a circuit when addressing a circuit or component modification. This can also be helpful when experiencing a component anomaly/issue when on the road and needing to continue home.
One last thought. If I remember correctly, power for your headlights comes from your ignition switch and passes through your light switch and dip (high/low beam) switch before arriving at your headlights and (depending on how you have wired them) driving lights. Depending on the type of headlights installed, a substantial amount of amperage will be passed over very light wiring. If you haven't already done so, consider installing (3) relays to bring fused power to your headlights/driving-lights directly from your alternator/generator/voltage-regulator. This would allow a significant reduction in power passing through your original thin-wired circuits and components to that needed for switching the relays with an improved probability of extending circuit and component longevity and reliability.
Enjoy your Healey,
Ray(64BJ8P1)