I think you might be stuck with it man. One of the pit falls of owning old cars.

I guess it could be, but there's not much padding behind them to hold smells. Could also be the soundproofing wadding behind those masonite looking boards on the firewall.

I even put thick sheep skin covers and also tried a custom synthetic vinyl seat cover and that didnt do the trick.

Someone told me it could be the roof lining as well?

I reckon it must be the seats themselves if you come out smelling like an old car. remove one, turn it upside down and have a whiff?

240K coupes had reasonable seats for the age of the car - sort of similar to the 240Z's seats. Maybe you could wash them while they are out of the car. I've done that with later model cloth seats, but with a vinyl seat it would be harder... you might have to look into getting them reupholstered and repadded? Or get some new seats.

How do you get rid of the old car smell?
changed the carpets, cleaned the interior, new seat covers, nice air freshner and it still stinks!!!

I hate going out using my old car... fresh and clean then after you come out of your car you're worst smelling than before you cleaned up!

how did you guys overcome this?

just tell everyone to cover their nose when ur passing?