There are lots of headsets that will free your hands for the steering wheel and shift lever; but most of them, particularly the tiny wireless Bluetooth models, just don't work well in a noisy ragtop.
The BlueParrott B150 RoadWarrior from VXI was invented for 18-wheelers, but it's great for Fiats, jeeps, tractors, forklifts, lawn mowers, construction equipment, or any car with a high-revving engine and/or loud exhaust. It also works indoors.
Its receiver will cover your ear, and has high output to overcome road, wind and engine noise.
Its microphone is a high-rejection noise canceling design, combined with a long microphone boom and wind screen. This minimizes transmission of background noise. Your voice is loud and clear.
Available at truckstops and HeadsetHouse.com http://www.headsethouse.com/vxiblb1blhef.html. DISCLAIMER: HeadsetHouse is my company.