Fuse block advice
I wouldn't replace the original fuse block - especially on a '76.
Make a list of exactly the items you want to add, how much power they will draw, and whether they will be drawing power with the engine running, or the key in accessory or run, or the with the key off.
Then we can figure out the most appropriate locations to add the circuit. It might be a spare fuse location in the existing fusebox, it might be an auxilery box, etc.
Here's a simplified diagram of the '76 power scheme.
An explanation of how it works is in this post.
Note the fuse box has some fuses that are always hot, and some that are on hot when the key is in run or accessory.
Be aware there are some circuits without fuses or circuit breakers, and others where the breakers are incorporporated into the switches.
See what 67Dart273 says.
I wouldn't replace the original fuse block - especially on a '76.
Make a list of exactly the items you want to add, how much power they will draw, and whether they will be drawing power with the engine running, or the key in accessory or run, or the with the key off.
Then we can figure out the most appropriate locations to add the circuit. It might be a spare fuse location in the existing fusebox, it might be an auxilery box, etc.
Here's a simplified diagram of the '76 power scheme.
An explanation of how it works is in this post.
Note the fuse box has some fuses that are always hot, and some that are on hot when the key is in run or accessory.
Be aware there are some circuits without fuses or circuit breakers, and others where the breakers are incorporporated into the switches.
