Found parts in my 904 Pan

Hey everyone.
So yesterday I was in my shop working on my car (74 Scamp with a 360 & 904 with shift kit set up). I just replaced the voltage regulator so I hopped in and revved it in park to watch my volts. And the car all of a sudden surged forward and made a clank noise. I investigated and reverse is gone, but when it's in neutral it drives forward like it's in first. And in park it tries to go forward but then stops and makes a clank noise. So I jacked up my car and pulled the transmission pan off to find a bolt and what I believe is part of the intermediate band. Im going to finish dropping out the trans today and try and see if anything else is broken. I figured I would ask for advice here sense I have never opened a transmission. I'm trying to figure out if it's worth fixing the 904 or swapping over to a 727. I have a 727 that came with the car but it came out of a truck and I don't know the condition. So I need to figure out what I would need to swap to that transmission or fix 904. Any suggestions would be great guys. Thank you

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