Gary, The thought behind the convert. series in NASCAR was that the fans could see the drivers working the steering wheel like at the indy car races and the hotrod races. It was also a way to sell more tickets having a seperart race than the hard tops on a different night.
Aeodynamics was not a problem because the ragtops and the hardtops did not race against each other, altough in the last few years of the circuit there were a few races called sweepstake races when the hardtops and ragtops ran in the same race, but each division had a winner.
When the factories backed out in mid 1957 and money was drying up,for 1958 some teams built cars called zipper tops, Cars could be raced as converts. on Saterday and a top was bolted onto them and raced as a hardtop on sunday.
The convertible division in NASCAR only ran from 1956 untill 1959 and Darlington ran the Rebel 300 for a few more years as a once a year ragtop race. But in the four years of the convert. division, it was some of the best racing NASCAR has ever offered.
JUST A MIDNIGHT CRUISE DOWN THUNDER ROAD!!! TOM DRUMMOND MIDWEST DIRECTOR 57 FORD INTERNATIONAL