Any engine could be ordered in the full size car (435 horse 427 down to the 185 horse 283). What was on he sales lot was the personal choice of the sales manager. He ordered most cars with a 283 two barrel PowerGlide because he assumed that was what most of his customers wanted.
A three speed manual transmission was the standard though by 1965 it was passé to have a manual transmission. A four speed manual transmission and the PowerGlide or TH400 were extra cost options. The four speed was fairly rare compared to the PowerGlide, but it was more common than the three speed was in 1965 due to it's association with racing.
In 1965 there wasn't a Camaro, it was the second production year of Chevy's new Chevelle, and the Chevy II was now offered with a 283 or 327 SBC engine (but not to be found on the sales floor most of the time, as it was still considered a second car or an economy car), and the Corvair was just redesigned in reaction to Ralph Nader's alleged expose on imagined safety issues (testing proved the car was safe as delivered with good tires, but but bad press caused GM to scrap the economy car image and turn to full IRS suspension which was a real plus in handling: but substantially raised the cost to make the car). The two door sedan full size with a 427 was still one of the hottest cars in GM's stable and was considered an alternative to the BBC powered Chevelle or GTO.
Thanks Paul and the rest. Not sure now if the 4bbl was original to the car. The engine seems to be but it might be possible that the intake manifold and and carb were switched out. It has a CAR"BURE"TER (or so it says on the carb) with an electric choke on the pass side. Could that make it a later carb version? I cant find any other numbers on the carb except 1672 on the top back. Thoughts?
The Rochester QuadraJet carburetor was introduced on top of the new for 1965 Mark IV BBC engine (396 in '65, 427 in '66) but they didn't appear on the small block until 1966. Your period correct four barrel on a 283 would have been a Rochester 4G on a manifold made to accept only that carb. No one liked that carb and every one hated the intake manifold (a maze of right angle passages) so an Offy or Edelbrock intake and a Carter AFB or AVS would have been more common a swap. the Holley didn't catch on with most Chevy owners until 1967 due to Holley's association with Ford.
But over the past half century any carb and/or intake manifold may have found it's way onto your engine. As far as that goes the 283 may have been replaced at some point in the past as hey didn't stand up well to pegging a 10 grand Sun tach, and may have been replaced in the past.
Dave, it sounds like you have a Carter WCFB which was available until 1965 from what I've read. They can be delicate and tough to work on, and some people just don't like them. It's an evenbore, and I think uses the same manifold Big Dave mentioned for the Rochester 4G.
Anyhow, welcome and enjoy your new ride!