I use an outdoor carcoon on my '88 and cannot fault it. It has survived two winters with snow, wind rain etc., and not a drop has passed through. It even dries the car when put away wet and keeps the cover away from the paint. Another major benefit is that the windows can be left open a touch to aid ventilation for the interior. It would even resist the huffing and puffing of the first two big bad wolves and maybe even the third because it is so flexible. BTW I've no connection with the company other than as a satisfied customer.
link here but I bought mine from the UK agent. You will need a power supply to run the fans.
Carcoon USA - Car, Truck, Motorcycle, RV Airflow Protection Bubble
cant check this link to photos in work so hope it works
Picasa Web Albums - noel - Carcoon
Oh and it keeps your battery trickle charged