The fuses can easily be replaced with inline blade type fuse holders. Just do 1 fuse at a time. Cut the wires right at the old fuse box, add the new fuse holder. Solder and heat shrink tubing. move to the next set of wires. Repeat till all done.
On the safety relay. It can be replaced with a standard lighting relay, the one with 5 terminals, as far as the safety interlock on the starter. Hook the yellow wire to terminal 85, hook the black wire to 86. Hook one red/wite wire to 30 the other red/white wire to 87A.
On the headlight side, does your bike have a headlight on/off switch? In the 79 diagram I'm looking at you just leave the blue/black at the safety relay unhooked. This lets just the headlight on/off switch control the headlight.
That doesn't look right. I think at the reserve lighting unit you need to unplug it and jumper from the blue/black wire to the yellow/blue wire.
Maybe some one who has a 79 and bypassed the safety relay's headlight function can better describe the how to.
Leo