Roger, I can't tell for sure from the photo, but the first terminal on that block where the blue wire feeds in looks like it may connect through to its mounting bracket. I would not use that terminal if that is correct, since it would normally ground when mounted to anything metal. Instead, you could use the first fuse terminal as the feed point, and jump to the next. But in fact, since that block has a cracked end - on the right - the insulator material is probably brittle, and to echo Bart', I would not recommend using that particular block.
It would be better to get a new block with an appropriate feed buss, such as made by Blue Sea Systems, for example:
6 Glass Fuse Block. They also have fuse blocks that use modern blade fuses, and choices for the number of circuits. If interested, look around their website, find a part number for a style that you like, and shop online at multiple sources for better pricing. Their blocks are generally better made than some of the no-name, foreign-sourced fuse blocks that you may see online.
Any high current circuits (typically lights, horns, etc) would benefit from using point-of-load relays as Dave suggested, although for best protection, they should be fused in their power feed, in any event.
Doug
