My 68 T/C wagon was ordered with a 440/4bbl motor and dual exhaust, build sheet shows this. It don't recall if it originally had HP manifolds, since the original motor and tranny were yanked for a Duster race car before I saved it, I will check the build sheet to see what numbers the exhaust manifolds had. But there was a big box of misc parts that came with the car, and I was told they were the parts off the 440 that the race car guy did not want. And there were a set of 68 date coded low flow log manifolds in there.
As for the difference between a 350 and 375 horse 440...mostly it was cam, carb, exhaust manifolds.
That is a gorgeous car, and loaded with almost every option except, disc brakes, cruise, and dual A/C...That is a fair price for that car I think.