If you have a TR7 then the normal replacement battery is a 075 which gives 530 Amps for a cold start. However, the tray is wide enough to fit a 096 which gives the much larger 680 Amps in a cold start. You will find these batteries readily available on e-bay often with no carriage costs, as they are used in Transit vans etc.
Sometimes the TR7 V8 with the front battery is fitted with the 038 model with a 320 Amp cold start as the height available isn't enough for the 069 which the V8 needs. As a compromise you can fit a 057 which has a very similar cold start current but significant larger capacity at 45 Amp-hr and it still fits into the pan.
If you have increasing problems with the pop-up mechanism for your headlights, which might remain down but they do light up, then first try tapping the relays as they must both click to operate the headlight pop-up actuators. Do carefully check the wiring in the engine bay to ensure the bullet connectors are making proper electrical connections and that the earth connection is sound. Another thing to check is the cut-out connections which you will find close to the fuses and relays.
Either switching the headlights on or operating the headlight flash should result in both relays clicking and the lights popping-up. If a headlight light sticks up and does not pop down this could be either malfunction of the relays or poor wiring connections.
It is important here to check the individual wire connectors and not the 3-way connector. If the connectors are corroded, loose or have a poor fit a quick fix after removing the corrosion is to add a narrow piece of kitchen foil to improve the connection!
It appears that the horns tend to fail after 35 years of installation and second hand ones are in short supply! Low cost FIAMM replacements, matching the original designs, are easily sourced from e-bay.
Do you have poor turn indicator canceling problem in your TR 7 when it is difficult to see the dashboard turn indicator pilot lights in bright sunshine?
A very simple solution is to add a buzzer additional to the wiring harness. Simply connect a 12 V buzzer from RS Components across the flasher repeater bulb on the side panel in the boot and extended the wires through the bulkhead so that the buzzer sits on wires at the bulkhead behind the passengers head. This now gives a gentle buzz as the indicator flashes to remind one every time the indicator stalk switch fails to cancel after a turn. If this buzzer is located in the boot it works when stationary but road noise unfortunately masks the buzzer sound.
One can extend this to both turn indicators using two buzzers and a three wire connection with a common chassis or earth return. The other option is to connect the turn repeated bulbs with two diodes onto a single buzzer.
Note you can also arrange this by connecting into the front indicators and position the buzzer(s) under the dashboard.
ALTERNATOR and STARTER
When fitting a new alternator for the TR this is a left hand one although it goes on the RH of the engine. (Please be aware of this if making an e-bay purchase)!
If the starter motor fails to engage it may require repairing wiring corrosion around the starter motor leads and also at the ignition switch, as it is not necessarily the motor which is at fault.