I'd say first figure out if the low compression is because of valves or piston/ring issues. Repeat your compression test with a few squirts of oil into the cylinder. If the compression is higher than dry, you have a piston/ring issue. If it is the same, you need to redo your heads.
As to the JY motor, it's always a gamble unless you can find a for sure low mile engine...
As for the rebuild, can you afford a crate motor? These is almost always your best option, though more expensive than a kit.
Remember that a rebuild costs more than just the price of parts. A good overhaul includes a tanking (clean the block) machining and tons of little things you don;t get in the kit (plugs, wires, bad sensors...)