Wow, ok there's a lot of good information here guys.
I was thinking of adding fields for peak position and number of weeks at the peak.
See The Whitburn Project : 120 Years of Music Chart History.
I actually ran across that last night at about 4am. I found the spreadsheet at
http://bullfrogspond.com/#There is an amazing amount of information in that sheet. Now I just need to come up with a fairly easy way of getting that info matched up with my tracks in MC. I kind of like the dummy file idea for the purpose of having the info available in MC even if I don't have the track. The matching up with the tracks I do have with the data though seems like a bit of work to do within MC but not totally unreasonable I guess. I'm thinking I might export my entire MC database and bring it into excel. Then come up with at least a partially automated way of matching tracks to data. Then just import the matches back into MC. Only thing I'm worried about is spelling errors and slightly different naming conventions and matching those with the data, I guess there will some manual work either way.