I think GM started putting those covers over the rag joint in about 1974 but it may be 73. I was working in a Pontiac dealership in Waco then and the factory rep said it was because rocks were getting caught in the rag joint and binding the steering.
The quick key is that there are three different A frame bushings for Chevelle size GM cars and the Camaro/firebirds and by matching the upper bushings you can hit it pretty close.
The Moog K5196 Fits most pre 70 Chevrolets 67/69 Camaros and up through 72 Chevelles. I'm almost positive that is not what you have. They are quite a bit smaller and shorter than the later units.
The K6108 fits 70/73 Camaro and 73v Chevelle among other vehicles
This subframe/stub might be what you have if the upper a frame bushings look like this
and the flange goes in flush to the A frame.
The 74 and up units used a bushing that looks like this With the little nubbies that hold it off the A arm a bit.
Which ever bushings you have in the upper A arms should determine what year of frame you have and you should be able to get parts according to that.