[HO455]

Like most things 50 years old parts have evolved and been superseded. The letter prefixes on fuses relate to size groups, voltage ratings and many times relate to how fast the fuse will blow at the rated voltage and amperage. Some fuses are rated as "slow blow" meaning they will tolerate over current conditions for longer periods of time. This link will help guide you to suitable replacement fuses.

https://www.optifuse.com/crossbus.php

Let's not forget that in the world of fuse protection our trucks only had the crudest and simplest form of protection from the factory, since that was all that was needed. No sophisticated electronics here. So if the voltage and amperage rating is the same, the size is the same and the internal element is the same basic size and shape the fuse will provide the all the protection need for one of our stock trucks. How many of you have bought a running driving vehicle only to discover later one of the fuses had been replaced with a gum wrapper?
If you have added aftermarket equipment then be sure to fuse it according to the manufacturer's requirements.