I know that the sales literature indicated that it could be the Rochester or the Holley carburator. I don't recall ever seeing a Rochester on a 325 horse 396 back in 1965 however.
It took several months (Feb to May) for me to eventually receive my Impala. My dealer here in Saginaw, Michigan submitted my order shortly after the release of the 396 engine in February 1965. After two months (around middle of April) the original Feb order was returned to my dealer for "reconsideration." The dealer told me that because of demand, the 396 engine was being restricted to the new Caprice line of Chevrolets and I would have to resubmit my order and go to the end of the line.
At the time I was a senior co-op student at Saginaw Steering Gear Division, General Motors Corp. I went to the Sales Dept at Saginaw and asked the Chevrolet sales person if he could help with my order. I also wrote a letter to Semon E. Knudson (Vice President - Chevrolet) indicating that they were ingaging in false advertising because the most recent adverisement for Chevrolet in that week's issue of Time Magazine listed the new 396 as being available in the Caprice, Impala SS and the Impala.
I asked the dealer to resubmit my order. Two weeks later my seafoam green Impala with 325 horse, 396 engine was sitting at the dealer. I never found out who or how my reorder got expedited.
I sure wish that I had kept that Impala.