Engine not starting or cranking, where do I start?

[TX58]

My 58 with the 283 V8 doesn't start or even crank anymore. It started just fine a couple of weeks ago. Im still putting it together so it's not been driven just started here and there. It's wired to factory specs using factory type harness. It doesn't crank when I turn the key. I can start it by bumping the starter but it doesn't stay running, just cranks up then stops. Where do I begin to start checking the problem? The battery is new and charged and I just replaced the starter thinking that could be the problem. Still the same,how do I go about checkling each key component ? Does anyone have a diagram of the ignition and light switch wiring?
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