I have a '77 Aspen Wagon, and I am in the process of updating/modernizing the main electrical harness. My choice is to have all under-hood connections separate from the main harness, and only let the wires returning from the main harness activate under-hood relays. The Aspen harness has some main circuits protected by 'fusible links', and as I have some bad experiences with fusible links, I have chosen to replace them with MIDI-fuses. (also used on late-model Mopars) They are so-called slo-blo fuses, that can accept an overload in the circuit for some time before they blow, just as fusible links do. I route all power through a fuse-block from Blue Sea Systems intended for marine use, but having a water-proof fuse block is my personal preference, there are many similar systems for cars. Except for the starter and starter relay wires that are heavy duty wires already in the Aspen harness from the battery,
all other wiring from/to alternator and battery are led via the fuse block, where those wires are fused before feeding the main harness through the firewall into the car. The block also have ordinary spade fuses for el-fan, HEI, lights + +. Mounting it this way, the only current going through the main circuit are those carrying a low load.
There are also alternative inline slo-blo fuses from Littelfuse to replace the fusible links, but I guess those are more expensive, and I am not sure if they have any visible indication that they are blown.
Cable inline fuses
Re. fusible links in this forum:
Fusible links
Blue Sea Safety Hub 100
Fuse blocks
The internet is full of similar products. My advice is to take your time, orient yourself of all options 'out there', and then sit down and design your new system seen from a safety standpoint, with all access points easy to service, and easy to shut down in a hurry. I also have a complete spare Aspen harness that is being modified to suit the new setup.
And for all those of you who are allergic to marine products, Blue Sea have exactly the same product line-up in their heavy-duty vehicle division:
http://terra-ps.com.
Olaf