I only have the figures in SI-unit:
Coupe: 215 Liters (7.6 cu ft)
Roadster, closed: 184 Liters (6.5 cu ft)
Roadster, topless: 102 Liters (3.6 cu ft)

For conversion:
1 Liter = 0.035 cubic feet
1000 Liter = 1 cubic meter = 35.315 cubic feet.