You could get posi (RPO G80) on any year Caprice, as long as you have the 8.5" ring gear axle. It is not specific to engine size. Both of my 94's are factory G80 cars. My 91 was not, because it had the 7.5" rg axle. I bought an axle from another 91 with a 305 that was a G80 car.