Corvette was always a road car not oriented to drag racing so few had a posi rear end as that affects how a car handles in turns. With a the advent of IRS in 1963 that pretty well sealed the deal on drag racing as the IRS didn't appreciate hard launches. So very few Corvettes had a posi when new. The limited slip rear end was mostly installed in big cars with a trunk full of product that a traveling salesman pedaled from town to town in all weather. That car needed a posi to negotiate dirt roads or snow. That is why most posi units were in a full size. Not for drag racing, as they were too weak for that (I blew one up a week behind my 409), but to cut down on wrecker calls to get unstuck and back on a paved road. Early limited slips are useless as they had a coarse spline on their pinion (17 splines) compared to 1963 and up 26 spline yokes which can transmit more torque.
This was because the Chevy was the last car in GM 's fleet to get a V8. Prior to 1955 the biggest baddest engine you could find was a 235 six (three main caps and drip oiling unless it had an PowerGlide, then you got an oil pump). The 235 was Chevrolets answer to the Hudson, the Ford flat head, and every other company that made cars with bigger more powerful engine (it was in production from 1929 to 1962). Without any power there was no need to make things like the Borg Warner transmission or the rear end any stronger. The 265 V8 SBC introduced in 1955, and the all powerful 283 introduced in 1957 began breaking parts as fast as you dropped the hammer on a hard launch. That is why the posi was modified in 1963 (with the introduction of the 327) to make it a bit stronger.
There isn't a drop out ten bolt early Chevy (1939-'64) rear end that can withstand modern SBC power never mind the axle twisting torque of a big block (includes the 348 and the 409). Hence every one wants a Ford style nine inch (1957-'86) rear end made by the aftermarket since the Ford rears are no stronger than a Spicer ten bolt from 1965. Spicer 12 bolts and the Dana 60 is what most people that don't have the power sucking nine inch use to replace the weaker six cylinder power train from before the eara of muscle cars (1965-'71).
A restorer looking to make a white glove clone of a car he isn't old enough to remember will pay for that posi for his 1958-'63 'vette. Even though they rarely if ever had a posi from the factory. He wants it because every one knows it has to have one, even though with any size tire and a modern power plant he will break it. I had a 1958 'vette that I rebuilt and all of the parts for the suspension except the rear passenger side radius traction bar were off of a full size Chevy. No stronger, no better.