This would be a good time to make a couple of very nice modifications.  I absolutely  believe in relay switched headlights and the addition of a horn relay and attendant horn wiring mod.  Also a good time to clean up any cobbled up accessory wiring and change out the glass fuse panel to an ATO type. 
I made up some diagrams for these and other mods which I'm happy to email.  Just PM me with your email addy if you are interested.  None of these mods are terribly difficult but make the car a lot nicer.

Definitely add the headlight relays.  Modern bulbs draw too much power and you'll trip the internal breaker in the headlight switch without them.  Its pretty unnerving to be driving at night and suddenly loose your headlights.

I did not change out my main fuse panel.  Instead I added a couple circuits fused where the relays for those circuits are located.  An auxiliary fuse panel is another option.  Not pushing any one of those three options, just saying there are options.  What you ultimately do may depend on how much non stock wiring you plan to add. 

Speaking of which, if you haven't already, now's a good time to upgrade to a better alternator.  Stock I think are only around 50 amps output.  You can get a basic 3G and get 90 amps for not much cash or hassle.  I did that about the same time I rewired my car.  It drives my stereo, etc. with no issues now and my headlights are brighter than the ones on my F250 with just regular halogen bulbs (Silverstar I think is the name, made by Sylvania I think).
 

Make sure  the new alternator’s  ancillary wiring is upgraded to its output.
On my car I tried to upgrade individual circuits but the deeper I got the more issues I found, so I stripped out all original harnesses and put all new wires in my 68 when I went to a 130 amp 3G.
The o/e wires were in sad hacked up and corroded condition from previous additions over the past 53 years.