Sons 300m and I need help please!

I think it is done.
I put the front end together and started the car again.
Running very rough and sounds like a rod knock but the noise seems to be coming from the top end of the motor, not the bottom.
Not sure what it could be or if it is even worth trying to fix at this point.
Internals in that motor are hard to get to and I don't have the shop setup to drop the motor out the bottom.
I am at a dead loss. Hate to scrap the car but I don't know what to do next.
Son is devastated. If we scrap the car, wrecking yard will give us $100 or so.
That is a big loss on an immaculate 2001 300m. And then what to do about his transportation. He is 16, and started Running Start this year so he is in college and has a part time job and starts a new part time job Wednesday. Sometimes I hate being the responsible adult...

I'm sure you know someone with a cherry picker...they put those 3.5's in everything for 10+ years. you can't tell me that LKQ or a local pull a part can't find one with the same ECM/tuning that would swap into the car.