914 -engine sizes- fit/wont fit???, Technical HELLLlpPPP Options

[Boldylocks]

First, I'm the owner of a 73 914 with a 1.7 liter engine that has bent/broken intake valves. I'm not a mechanic, but the cost to repair this part seems to be as much, if not more, than finding a running engine and putting it into the car.
With that said:

Can I 'drop' any 914 engine into the car??? 1.8 -2.0??

Is the mechanic correct, will it cost me nearly the same amount to simply find (FAR FROM SIMPLE) a running engine and have it put in the car???

Can I 'drop' any of the larger engines into the car without any problems???

___ next level questions_____

Anyone with any ideas of the causes for a 'big bore' engine to RUN HOT . there is no thermostat connected to the engine and after about an hour of running it starts heading into the red zone.

-for direct contact: Rfranklin@price-entities.com -during the day (pacific time), Riccif@cts.com -at night.

I would really really appreciate anyones help/response. I'm always greatful to this board and point eveyone I know in its direction. My current 914 was purchase after many hours of discussion on this board and it is a gem. The ENGINE was damaged due to mandatory driving on the face of the MOON in order to get to work for nearly 3 months (streets on my way to work -were pothole infested- caused serious damage to exhaust/engine -though again, according to what I have learned I simply have an 'intake valve -bent/broken' issue).