Thanks.
Used 1 part bleach to 8 parts water( more bleach could damage threads of seats) to get rid of any mold/mildew then apple vinegar and lots of scrubbing.
Luckily the rear seat and passenger front bucket were just filthy with no other damage. Passenger bucket should clean up nice also but drivers is fubared.
Still deciding if I want to re-upholster front buckets in future( have done 4 over the years) and early a buckets are a pita to re-cover correctly and don't wanna pay shop. Might end up going with pro car low back buckets.
To start thou just gonna throw cover on drivers side and get her in the wind.