I need help! I have a 1964 Chevelle Malibu SS with the 283 and auto.

A few days ago, I went out to start the car. when I turned the key to start it nothing happened for about a second then the car started. It was almost like I had not turned the key far enough but I knew I had.
Drove it to the gas station and it would not start when I tried to leave. I noticed the blower motor for the heater/defrost did not come on when the key was in the on position, however, the gas gauge registered and the interior light dimed slightly. When I turned it to start, the temp gauge pegged and the interior light got brighter. No clicking or other noise at all.
Went back that night to tow it home gave it one more try and it started right up. I drove it home and it started 3 more times in a row and then back to nothing.
I have replaced the iginition switch and cylinder as well as replacing the starter and battery cables. Still nothing. I swapped the battery out of another car...still nothing.
Anyone have any guesses as to what is keeping this car from starting? It's like the starter is not getting a signal from the iginition switch.
Any help would be appreciated.
Thanks,
tom

Not sure on a '64, but I would check the neutral safety switch if it has one, then ALL the major grounds. Again, not sure where those are - but given the finicky nature of it, I'm betting you've got one or more loose connections, probably the grounds.

Rather than unnecessarily replace a bunch of stuff that is not the problem, I would get a volt meter and find the real problem.
Start finding out where you do have power and where you do not have power.