Interior work is where I've seen the most false economy in restoration projects. People buy cheap seat foam because it's just foam, then wonder why the seat collapses within two years. They buy cheap headliner material because it's hidden, then have it sag and yellow within a year.

Quality foam is available from suppliers who reproduce original specs. Quality headliner material is available from suppliers who know the difference between a car's original specification and whatever is cheapest to produce today. The cost difference between cheap and correct is usually not dramatic; the difference in outcome is large.

The interior is what you experience every time you drive the car. Invest in it commensurately.