black plugs on the dash are probably factory. Toyota didn't always fill the holes when they went to the next model year...
Factory radio is AM only, and I think sports the TEQ logo.
'74 is a good year, transition F engine (F.5) with the better oiling system, highest number of FJ40s were imported that year. Also has the 4spd.
IME, Haynes manual is a good cheap manual that covers a surprising amount of info on the vehicle and is reasonably accurate. The Factory Service manuals are even better, you just need to ask around to check availability. It's been a while since I ordered mine, but they didn't seem to have any problems getting them to me.
No idea on the Warner carb kit, usually the Hygrade or Keyster kits come recommended on the forums. Let us know how you like yours.
Looks like you found a nice rig. What are your plans for it? Are you going to drive it and work on the rust (doesn't look like much) as you go, looking for a stockish build eventually?