I knew that 64 was first but I like what they did in 65 to sharpen the lines. It was all straight lines and angles. Found a 64 on BAT, below.
I actually bought a 66 GTO body, in high school, and put a Chevy engine in it. The motor mount pedestals unbolted and the swap to Chevrolet from Pontiac was easy. It was basically a Malibu frame with GTO sheet metal. I bought the car half-stripped down, no windshield, interior, engine, transmission. It was a project. Every day was winging it, no clue what I was trying to do. My English teacher thought I was deep in thought about class material but I was really just making a list of all of the parts I needed to get.
I picked up a 63 Bonneville 4 door also, for free from a friend's family, after I wrecked the GTO. 389 and four speed automatic. That was a fine machine. I miss those old heavy metal cars. Even the 72 Ford LTD with the 351 Windsor. Smooth motor.
https://bringatrailer.com/listing/1964-pontiac-gto-23/