The pier on the left is the design used on both sides of the shipping channel on the 1954 Sunshine Skyway as well as the major pier on the north side of the shipping channel of the 1971 span.
The pier on the right was originally identical to all the other major piers but the design as shown represents the repairs made to the pier.
Now here's a picture of the old Sunshine Skyway support piers when I went out on the Steven Thomas, an excursion boat that used to offer trips to the old Sunshine Skyway several months after May 1980 (I went out there sometime in 1981, that's when the photo was taken):
Top photo: Drawn in Microsoft Paint depicting the old Sunshine Skyway main span piers as seen by me during my younger years.
Bottom photo: Taken aboard the Steven Thomas in 1981