I took apart my oil pump today to clean it and inspect the tolerances. The haynes manual states the rotors should be mark so they can be placed back the way they were found, which I did but the mark end up rubbing off during the cleaning process. Is it essential to place the rotors back the way they were found or can I improvise? Thank You.

It may not be the ideal but I wouldn't lose sleep on it. There are some motors out there where it can cause a vibration due to there being a shaft behind that need to be aligned just so- not hte case with Subarus AFAIK

i've never worried about it and have mixed/match oil pumps/rotors/motors with no issues.