Based on the Hamtramck web site (https://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1968/68_Coronet0008.jpg) the R/T came standard with bucket seats. You could order the "Optional" full-form bucket seats with a fixed center cushion and fold down center arm rest.
I don't "THINK" you could order a bench seat on an R/T from the factory
@69Coronetrt would be more knowledgeable on that.
On your fender tag what is the numbers under the top line a and b
I don't "THINK" you could order a bench seat on an R/T from the factory
@69Coronetrt would be more knowledgeable on that.
On your fender tag what is the numbers under the top line a and b