I don't think this should be called an Amilcar 'Jeff' - That was a very similar but different car. The puzzle car is an Amilcar C6 owned and raced by René Ducreux, who built the streamlined body in 1948. Ducreux raced under the pseudonym 'Jeff' and I think this is where the confusion comes from.
This car still exists, restored close to original specification with a standard C6-type body. I believe the streamlined body built by 'Jeff' still exists, too