The old resin and cloth covered wire that was used in the early Ford days can crumble to dust after so much time. It's not unusual to have opens or broken wires, shorts to ground, and cross shorting from one wire to another. Shorts to ground and cross shorts can both cause a circuit protective fuse to blow. It sounds like the OP has a problem of that nature.
Dash lights are usually controlled for dimming through the main light switch but there may be a light for the key switch or a light in the glove box. I'm not sure about dimming on the 49 & 50 Fords though since my experience is mostly with the Mercury cars. In any case, the wires with the most exposure to the elements are the ones to check first. The tail and stop light wires travel all the way to the back of the car and can be exposed to some moisture and may run close to a lot of structure that will act as a ground path. If specific wires are isolated by disconnecting them at both ends of the circuit, it's easy to check them for shorts to ground with an ohms meter. Cross shorting depends on the circuits each wire is in a run with so it takes more time to find. It may be easier to replace the electrical harnesses for the circuits that are having problems and especially if the insulation is in poor condition. Harnesses are available from several sources.
For disconneting the terminal blocks that Ford used in the 8BA era, a person can generally find a tool that can be wedged into the gap of a socket to aid in removing the pin from the socket. They can be stuck in there pretty good but I've always managed to get the pins out without breaking the wire.
