I changed the speedometer cable in my car and now it refuses to start. Any advice?

I have a 1985 Chevrolet Monte Carlo. It was originally a 4.6 fuel injected, the owner before me replaced that with a carburetor fueled 307. they did however leave the 200c transmission behind. I replaced the 307 with a 350 this winter which I bolted to the very same transmission. It ran fine however the speedometer and odometer had failed to function since two weeks after I purchased the car. I replaced the speedometer cable last week and now the car won't start. The voltmeter says 14 volts on the first notch on the key, I turn the key to ignition and it clicks once and then the meter and all the electronic components in the car go dead. To repair the cable, as I am sure you know, I had to take apart the instrument cluster to gain access to the cable, might I have fouled something up there or is it convenient timing for another part of my car dying? I am lost so any and all tips may help and will certainly be appreciated.