914 engine replacement options - Advice and Opinions please, What are my best and easiest options? Options

[UberElectricEagle]

Greetings,
I'm new to the 914's so please forgive my ignorance.
I have a 1972 1.7 with dual carbs (weber 34) that is slowly giving up the ghost. I'm going to keep driving it until it quits or I find a replacement motor. I'm trying to figure out what my best and cheapest option is to put a good and solid running engine in my 914. Yes, more power would be awesome, but just a working motor would be great too.
What I was thinking I would like to find is a decent and solid running engine that someone has removed from their car for whatever reason.
-What are my plain stock options? 1.7 1.8 2.0 ?
--Can all my 1.7 components switch over into a 1.8 or 2.0 or would I have to get some different items like bigger carbs or a different distributor?
-What kind of fair price can I expect to pay for a fairly complete and running motor?
-What could I expect to pay for a rebuild if I went with that option?
-Can I just use any type 4 engine (say from a VW whatever) and switch all my tins and components over, or are they set up differently for the 914?

I'm looking for all opinions or what you would think you would do so I can look at every angle here. Any guidance in the right direction or ideas would be much appreciated.
Thanks,
Sam