Things that go "CLUNK" in the night, Need help with a (non)starting issue Options

[poorsche914]

Recently brought home a '73 2.0 that has sat for 3-1/2 years. This is truly a case of "ran when parked" as I saw it running back then. (IMG:style_emoticons/default/confused24.gif)

I swapped the old carb for a new one, installed a battery, and turned the key to start. All I got was a "CLUNK" and the voltmeter needle bottomed out. Tried jumping it and same result.

1. The engine turns when rocked back and forth in 5th gear
2. Starter "whirrrrs" when posts are jumped
3. Traded starter and (+) battery cable from my running 914 (same "CLUNK" result)
4. Cleaned up ground connections on transmission ground
5. Tried a brand new battery... same results

What should I be checking that I have missed?
Car has a 914-6 ignition switch. When turned to START position, it does not auto-return to ON position - has to be done manually. Could the issue be in the ignition switch?
I have a voltmeter (somewhere) Guess I need to find it (IMG:style_emoticons/default/rolleyes.gif)

(IMG:style_emoticons/default/driving.gif)