66 wont crank, acts like battery is dead

Have you replaced the volt. reg.? Is your car a manual or auto (now and originally) It's possiable that it could be the volt reg, but since some of your other electrical acc. work, it would not be too likly (but still a good idea to replace it none the less). Why it won't start after you replaced the relay and starter is puzzling. The clicking noise you hear is the relay closing, so it's sounds like it works, but you still can't be sure. What I would try is getting a piece of wire (about 6" long) and a screw driver. Connect the wire on the "I" post on your stater relay and also to the post were the + side of the battery hooks up too. Now, take the screw driver and use it to jump from the + side post on the starter relay to the "S" post and see if it cranks and fires up. If it does fire up, then make sure to take the screw driver off when it does. Another possiably is that your ignition switch is bad, so test it to make sure. Test your starter as well. Just because it's new, doesn't mean it works. Let me know what happens when you try this out on your car, and if it still doesn't work then we can go from there. Now, as for some of your gauges not working; I would check to see if the little vlt. reg. on the back of your cluster is fried, as this is a common reason.

-Shaun

Can you pull the plugs and turn the engine by hand? If you pull them and you cant turn the engine....your engine is seized up. Your starter might be working, but just cant turn the engine.

Check all your grounds and make sure they are tight and clean.

ok I dont know if this helps but this is important:
My buddy just bought a bronco that was in an accident and had flopped on its side. I couldnt get it to turn over for hte life of me, even when jump starting it.
I got tired of screwing around with little stuff that i knew wasnt the problem in my case, so I swapped in a new (used) battery.....
...The problem was, that the accident had caused the battery internal damage (shorting out inside the battery).

So try and swap in a battery that you know is ok.

I had a similiar problem with mine but its an automatic so probably won't help. It may trigger another thought somewhere so I posted anyway.

There is a sensor on the shifter which requires the trans to be in park before it would start. Took me a long time to figure that dumb thing out by I am still very much a novice. If this was at once an auto then it may make a diff - don't think that applies to manual. Check the VIN to see if it was an auto.

Sorry I couldn't be more help

Since it clicks at the relay, I wouldn't expect it to be in the ignition switch. If it were mine, I would check the resistance between the positive terminal on the battery cable and the relay's power side. Sounds like you have insufficient power.