Player Attributes for Classic Rosters

[christopia]

This question goes out to any user who has created a classic roster. Playmakers, cursive, capa, Dr.J, etc. How do you determine what attributes you set for each classic player? Is it a best guess coming from your extensive football knowledge, do you vigorously look up old statistics and old 40-yard dash times (if this information is even available for old generations)?

My next question would be if there is a website or valuable source that has determined Madden attributes for every classic player in their prime, or for a specific year. I found FBG for current players, but not old players.

I've dabbled in many people's classic rosters over the years, but I'm never sure which set generally has the most reliable player ratings, since they all vary, and they all come from the mind of a singular person. To anyone: is there a classic roster set that you hold to the highest esteem when it comes to player ratings? Or is it a crap-shoot?