Production Information needed on a 1964 1/2 Convertible

Hello all, A friend of mine recently purchased a very early production mustang (March 31,1964) with a Vin of 5F08D106001 . The car was made in Detroit and is a convertible 4 spd car, red on red. We are trying to determine which Mustang it was in sequence. Does anyone have any ideas on this topic? Last week I was up in Detoit and visited the Ford Research Center, but could not tie down any new information. Any help from this community would be greatly appreciated! Mark