Welcome to the forum Kevin. Glad you joined in. The '61, '62, and '63 Buick Special was Buicks/GMs entry into the compact car market. Chevy started with the Corvair in '60. Pontiac, Buick, and Olds all used this basic size platform for their own model in '61. Buick/Special, Pontiac/Tempest, Olds F-85. They had two distinct frame/body packages. The Pontiac used a unit frame with bolt on suspension units front and rear (the Pontiac was the only one with a "Rope Drive" drive shaft, rear transmission (transaxle), and independent rear suspension mostly identical with a Corvair. Buick and Olds used a common front engine/transmission and live rear axle. Both the Buick and the Olds used a full frame versus the uni-boy Corvair and Tempest.
The Buick used two basic engines. The Buick V-6 and version of the Buick small cube (215 ci) V-8. I believe the Buick V-8s may have all been all aluminum, block and heads, but not sure if some were cast iron?? I believe the Olds (they used their own version of the same 215 ci small V-
were all cast iron, block and heads, but don't quote me on that. OK back to Buick.
The '62 Buick Special used a full frame, V-6 and small version V-8, more conventional front and rear suspension and front engine/transmission placement.
Body size. If you are familiar with a '64 and up GTO, Chevelle, Buick Special, and Olds F-85, the '61 thru '63 Buick Special is just a little smaller than those later cars. It shares practically nothing other than bolts and bearings (maybe) with the full size Buicks etc of the time.
'62 Special had two 215 ci V-8s. A two barrel 155 HP/220 TQ and a four barrel 200 HP/240 TQ version. Bore/stroke, 3.5X2.8. One V-6, 198 ci, 135 HP, 205 TQ.
3 speed, four speed and automatics were all available.
Your questioin about swapping the spindles etc with the same year full sized car I can't really answer. I would guess that they will not swap over. Just a guess but I feel highly unlikely.
Let me know if you have any more specific questions and I'll try to answer them.
I just wanted to answer that, if you are looking for a little bit different ride, to drop etc and customize, they do make a really nice platform to play with. But they are limited on aftermarket parts support. I would look up Buick special on the ol' interweb, and see what pops up. You might be surprised.