now what do I do

I have an 1970 340 in my 73 scamp when I bought it the guy told me it was rebuilt under 20,000 miles ago. he didn't know anything about the rebuild it was done by the guy he bought it from. so I decided to tear into it and find out for myself. had a few oil leaks to repair anyway. pulled the timing cover off pulled it up on TDC and found that the cam was 180 degrees off. Now I'm not a pro at this put the timing mark on the crank is facing up and so is the timing mark on the cam. and it runs just fine so did I do something wrong or the guy that rebuilt it.