Yes, but they may actually differ slightly in appearance and function. What suspension parts are you looking for? Things like steering linkage can differ depending on what engine is installed in a car. I-6 are mostly the same 64-67 But the Buicks used a V-6 as the base engine. Control arms should be OK, spindles should be OK, Brakes (with the exeption of Lug Stud size) should be interchangeable. Rear Axles differ but can be swapped.
Before 68, GM wasn't as interchangeable so be careful. Best not to mix and match tie rods, idler arms, and center link. You'll probably be OK if you source them all for a Chevelle. There may be some frame differences that necessitated the different parts, but it may have been lack of communication between divisions.
The 1964 A-body cars have some one-year-only items, like the upper control arm bushings. There were also year-to-year and model-to-model variations, such as differences in the center links. The hard points on the frame are identical for all 1964-67 A-body cars, however, so if you swap a complete suspension setup including upper and lower control arms, any 64-67 setup will bolt to your frame. All 64-67 A-body cars use the same steering geometry, so pitman and idler arms are the same for all (manual and power steering are the same length, but the pitman arm splines need to match those on the steering box). Note that this is unlike the situation on the F-body cars, which people sometimes confuse with the A-body. The front spindles all interchange from 1964-1972, as do the steering arms that bolt to the spindles, but there are two different diameters of bolts used so the arms need to match the spindles (or at least the bolt size in the spindles). Again, steering arms are the same for manual or power. Obviously disc spindles differ from drum spindles, but they can be swapped. Rear suspension differs based on the year and the axle style used.