How many were produced - '75 L82 4sp roadsters?
"I have a 1975 convertible L82 4-speed with air, PW/PS/PB, AM/FM radio, map light, deluxe silver interior. Car is mille-miglia red with black top. Have narrowed it down to 1 of 1057 produced and would like some help narrowing this down further with the given color combinations and options".
Unless you know the car was ordered with a close ratio trans and not the standard trans, you can't even get that close. There are no stats for color breakdown. At this point, your car is 1 of 2372 because of the L82. 
All 1,057 M21's went with the L82, but you also had probably several hundred more L82's go out the door with the Wide Ratio M20 and just no way to know how many of the total 8,935 cars with M20 were L82's. If you figure maybe 1,300 L82 4-speeds, you could run the percentages from there with your other options but when you do this you will find that almost every car is extremely rare due to some unique option or color. The silver interior on your car together with the other options and colors probably means that there were no more than a handful made exactly like it, or it could be the only one but everything will be a guess as no records of this kind were ever kept.
Yes they were all Warners in 75, but the standard tranny on the L82 was the M20 wide ratio with 2.64 low and unless you ordered the M21 2.43 low, you got the M20. Look for the tag on your side cover. If it's still there, will say something like AS*-T10 and then a letter; W for 2.64 low (M20) and S for 2.43 low (M21).
Several years ago a 1975 Corvette L-82 Survey was made. With over 66 1975 L-82s in the Survey. 38,465 1975 Corvettes, the earliest VIN# was around 19,XXX. Car build date was around March 21 of 1975. Some buyers waited 6 months or more for their car. Only 66 cars in the survey were heavily optioned cars. Since 8007 '75 Corvettes were painted White out of 38,465 cars, probably about 40% seemed like they were White cars. Another interesting thing was that it was pretty much an even split for 4spd cars vs automatic cars.

A letter from GM that was sent to an owner when he inquired to GM the same question you are posting. This "GM" letter is dated
November 12, 1975, so, at least at that time GM did know, but, out of 2372 1975 L-82 Corvettes, 2006 were coupes, only 366 were L-82 convertibles, since 3355 Millie Miglia cars made up about 8.7% of '75 Corvette production, 8.7% of "366" equals 32 Millie Miglia L-82 convertibles. This is just a "theoetical" number. Either way, ANY 1975 L-82 convertible is a "very rare" car.
Wow! Less than 1% of 1975 production were L82 Convertibles.
My car is a 75 convert L-82 with the M21 trans car no.431724 with a build date of 6/75. Bright yellow with med saddle custom int., hard top, gymkhana suspension, air cond, power steering and brakes, tilt wheel, dual horns, AM -FM radio. $1856 in opitions , destination $74, out the door $8467.10. 31k miles on the car and i got the car in 1992.
...just for info, 1975 Bright Yellow Roadster is one of the rarest L82's out there. 
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