Drain pineapple, reserving juice. Set pineapple and juice aside.
Combine egg yolks and salt in top of a double boiler; add reserved pineapple juice, 1/2 cup sugar, and lemon juice, stirring well with a metal spoon. Place over boiling water and cook, stirring constantly, until mixture thickens and coats the spoon. Remove from heat, and stir in crushed pineapple. Cool to room temperature.
Beat egg whites (at room temperature) in a large mixing bowl until foamy. Gradually add remaining sugar, 1 tablespoon at a time, beating until stiff peaks form. Gently fold cooled pineapple mixture and whipped cream into beaten egg whites.
Lightly butter two 2-cup metal ice trays (with dividers removed). Sprinkle the bottom and sides with vanilla wafer crumbs, reserving a small amount of crumbs for garnish. Spoon pineapple mixture evenly into each tray; sprinkle reserved vanilla wafer crumbs over top. Freeze overnight.
Let each tray stand at room temperature 5 minutes. Slice and serve on chilled dessert dishes; serve immediately.