So, the strategy is to rebalance the first of every year. The portfolio should contain the top 50 best performing stocks in the S&P500 from the previous year. Performance is measured as the total price gain (in percent including dividends) from Jan 1 to Dec 31 of the previous year. Each stock is equally weighted (ie 2%). Is that correct?
Here's something that's close. There isn't a good way to get the exact S&P500 but this takes the 500 largest companies by market cap (very close to the S&P500). Also, there isn't an easy way to get the exact returns from Jan 1. This uses a window of 252 trading days which is typically within a day of a full year (again very close).
Look at the record variable which shows the number of stocks. A lot get delisted during the year (the amount just goes into cash) which was a bit of a surprise. A lot of mergers and acquisitions I guess.
Depends upon where one starts this strategy but looks like over the past 15 years it would have returned only about half of the SP500.