In my truck I added an additional fuse block under the dash and ran my HEI wiring from there. It isn't necessary to add a fuse block, my I didn't have many spades left on the original so it was easier to do it that way then have a nightmare of scotch locks and splices. I figured my truck had seen enough of that abuse over the years
You can come off an unfused key-on hot and add an inline fuse, or use a fused key-on hot and skip the inline fuse altogether. Does this answer your question?
Here's a pic so get the general idea
