Starter wont engage

Sounds like you don't have a multimeter. I get them free w/ coupon at Harbor Freight and carry one in all my cars. Have saved me from a tow several times. The "click-click-click" is a familiar sign meaning "low battery" to anyone who has owned any car for a few years. In your case, more likely "bad connections". Years ago, my wife call me with that problem in our 69 Dart, so I drove there and measured a solid 12.5 V across the battery terminals while cranking. I moved the multimeter to the wire side of the BATT+ terminal and measured 5 V while cranking. Cleaned the terminals with the brush 67Dart273 shows and it fired right up. My wife thought I was a genius and one of our kids might have been conceived that night. Maybe you'll be as lucky. Haven't had that problem since moving to CA, plus I always spray terminals w/ anti-corrosion after a good cleaning. When I lived in FL and GA, white powder on the terminals was a constant problem, and ceramics (lead oxide) don't conduct electricity.

On the issue of "new to you" engine, initially siezed. A simple and good way to test the condition of the cylinders and valves is to turn the engine over by hand, either tugging on the fan belt or a socket wrench on the crank bolt. If you feel 4 good "air spring" resistances per revolution for 2 revolutions, that indicates your cylinders have a good seal. Even better if you really have to fight each cylinder and hear it slowly leaking down for >10 sec. Of course, easier to distinguish each one if a 4 or 6 cylinder engine.