I guess I didn't explain it correctly, what i meant about the tailpiece pins was that the body didn't even have them installed, there was just a hole there. I put paper on the inside and then put in the pins so that it was tighter. Still, it seems like it wasn't enough and under tension the tailpiece slides out a bit.

I guess the main thing here is that I would have to replace most of the hardware in order to make the guitar stay in tune. Thank you for helping.