first of al i find that jou must judge by jour own comfort , the main thing is jou need to have fun of this car and not let it rest in the garage , so if leather is more comfy and gives it a nicer look i would do it , the value whil not increase by adding leather , sometimes if the leather is a little bit worn it gives the car an even nicer look , thats why im purshassing a second hand interior , and not restauring it to new