well, since you have both sets of red wires running to fuse links on starter relay AND you have ( althought I can't see it on your picture, but per what you said ) the link runing on the other black line to the engine haress bulkhead plug, I'd say to conect everything like this:
Actually although I made it similar on my own car, later I analized and doesn't have to much sense have a dual fuse link on starter relay from the RED circuit coming from ammeter, because that will make to take too long to blown them out if a short appears ( I will modify that on my own car ). Neither have sense to have a fuse link on the black wire through the bulkhead to protect the circuits to the main splice into the cab if at the end the thick wire with the grommet will be still feeding the main splice is a short comes on. But if the car came with them is to use those, so wire them like factory did ( 74 diagram doesn't specify about cut and tape them, althought earliers do )
The other black wire we are assuming is the power to the heater relay ( wherever it is the relay, which I dunno ) is to conect it on the same bunch of black wires into the amm stud. All the amm stud wires will need to be clean and tight. I guess the black wire have a 20 amps in line fuse ( diagrams shows it ) somewhere.
Ok so you have the tach wires in place. So I have NO IDEA what could be the gray wire you got. Unless is some splice made by the last owner, some mod but by now is something I still don't know. I'm trying to imagine on some extra equipment I never have known on these cars carrying a gray wire.
Could be the gray wire the one to the VL limiter ? have no idea, should be black.... maybe it was spliced and got enlarged with this gray wire ? dunno. The Volt limiter wire gets sourced from ACC circuit. If you want to test it somehow?... you could check for continuity between that wire and the ACC provision on bottom of fuse box ( just right below the fuses row ). It should get continuity just with key in ACC ( or RUN )
Voltage limiter must get 4 black wires like the pic posted by
Bb70charger500 and each one is imposible to mix them up ( althought +12 volts wire and condenser can be reversed they are conected to the same provision ). +12 volts, ground, output to gauges and condenser
ALTHOUGHT the system can work without the condenser since is just a noise suppressor, and ground wire could be disconected because as far cluster is correctly attached to dash and Voltage limiter is tight againts the cluster, the limiter and the gauges could work ( but for safety better to have that ground wire attached, because the absence of good ground there, can burnt the gauges )
Payment... God... a real temptation and a good help at this moment, but no, don't worry, is a pleasure to me.
Searching parts for my Charger ?... I'm allways hunting for parts but my car is at this moment dissasembled over jackstands and being painted. Dunno if when reassembling will find something missed or broken ( I HOPE NOT!!!! ). I guess If I need something will start a WTB thread LOL.