Keep in mind that besides the 400 known Beatles album clues and backward masking of the Beatles records that indicate that Paul McCartney died and was replaced, there is some compelling evidence too. See the list of evidences I have collected below. Cumulatively, it's very compelling and strong when taken as a whole.
1. Faul is 3 or 4 inches taller than Paul. You can see it in his photos with Jane Asher. The original Paul was the same height as her, whereas Faul is a lot taller. That is physical hard evidence that cannot be refuted.
2. If you look closely at videos of Paul in 1966 and Faul in 1967 you can easily see that they are two different men. For example see the 1967 LSD interview he did where his face looks very different and elongated and his personality was aloof and arrogant, not like the original Paul at all. His voice and accent also sounded deeper and different. It could also be that a double was used in that interview because the real Paul refused to promote LSD which his handlers ordered him to, in order to promote drug use and degenerate society.
3. The original Paul could not play piano but he was great with the guitar, whereas Faul was proficient with the piano but uncomfortable with the guitar, which you can see in his videos. Faul looked very comfortable playing the piano, but awkward with a guitar. This is a major INVERSE between the two.
4. Paul preferred to live in London. But Faul preferred Scotland and called it his home, even though he supposedly grew up in Liverpool.
5. Paul was originally from Liverpool. But Faul does not have a Liverpool accent at all, according to Liverpool locals who listened to his voice. Faul's voice and accent are different from the original Paul if you listen closely to it. He has more of a Scottish accent than a Liverpool accent.
6. One of Faul's ex wives, Heather Mills, said that Faul had a big secret that the world could not handle, but was afraid for her life so she had to keep it secret. She said this overtly on TV. You can see many copies of it on YouTube.
7. According to rumor, Faul was arrested in Japan at the airport for having marijuana in his luggage. The Japanese government jailed him for 9 days because his fingerprints did not match the orginal Paul McCartney. The UK government had to work with Japan to get him released.
8. Paul's daughter and her mother in Germany sued him for extra child support in a paternity case. When the court had Faul take a DNA paternity test, it turned out negative. The mother and daughter claim that the person who took the test was an impostor. This indicates that Faul was the original Paul.
9. After Paul became Faul at the end of 1966, the Beatles no longer played before a live audience anymore, suspiciously. That cannot be a coincidence in light of all the above. It obviously means that they could not do live concerts anymore or else people would see that Paul was a different guy. Plus Faul was not accustomed to the guitar yet and needed time to practice and blend in with the band. Instead, they played only in the studio and they all grew their hair and beard long, to try to mask the change in Paul's face and height. It can't be coincidental. Given all the above, it makes sense and must have been part of the cover up. It's what you would do too if you were them, given the above circumstances. As they say, everything happens for a reason.
10. After 1966 the Beatles never played their original songs anymore. They started playing completely new songs. Usually singers are glad to sing their best hits from the past. But the Beatles did not, with the exception of the "Yesterday" song perhaps. This means that they could not sing their original hits like "Help!" and "She Loves You Ya Ya" and "I Want to Hold Your Hand" because it would be too noticeable that Paul was a different person. So they couldn't do that of course. In light of the above, it cannot be a coincidence and is understandable. If you were them, you would have had to do the same.
11. When Paul became Faul, he soon broke up with Jane Asher and got together with Linda Eastman, as if that was his real partner, not Jane. Again, taken alone, this may not mean much, but taken in conjunction with all the above, it's obvious why if he was in fact a different man by then.
12. Faul never went to his father's funeral too. Now this on its own may not mean much if it's on its own, since some people have bad relations with their parents. But taken in conjunction with all the above, it makes sense because if that's not even his real father, then he would not go to his funeral of course.
13. When John Lennon died in 1980 and Faul was interviewed about it, he was apathetic and nonchalant and only said "It's a dreg" with no emotion behind it. That's an odd thing to say if you lost your childhood best friend. Again, taken alone, this doesn't prove anything, but taken with all the above, it obviously means that they were never childhood friends because Faul is a different man from Paul. And they were probably not very close even when they worked together, and probably didn't like each other that much.
14. In several Beatles documentaries, when Faul enters the room, you can hear his close friends and associates call him "William" or "Bill". See Mike Williams from Sage of Quay or Tina Foster from the Plastic Macca blog for the exact names of these documentaries where you can find these clips. There are 3 or 4 of them. This is because his real name is William Shepherd or Bill Shepherd, according to the book "The Memoirs of Billy Shears."
15. There is a clip where Denny Lane is being interviewed (he played with Faul in his Wings band) and asked about William Shepherd. He then alludes to Faul's true name "Billy Shears". Hence he indirectly implied that Faul is Billy Shears, thus giving us a cryptic clue.
Now taken alone, each one of these might be able to be explained away, but taken cumulatively, they definitely constitute a strong case that Paul was replaced, if you think about it and look at the big picture. So it's not one or two things, it's cumulative evidence.
For more info, look up Tina Foster's blog Plastic Macca at
http://plasticmacca.blogspot.com