The reason why Chevrolet wasn't included in this article is because the brand didn't offer a 455.
I wonder how much more torque did the 454 offer compared to the cars in this story? The answer is not "the others didn't come close."
Your fuel mileage comment made me think about a friend's late 60s (67-68, I think) Buick Electra 225. With five of us and our luggage, that car made the trip from the Treasure Island Naval Base near San Francisco to the Dallas/Fort Worth area averaging 19 mpg! He had been bragging about his mileage, but none of us believed him until the first couple fill-ups on the trip. I can't remember the engine size, but the car must have had some very tall gearing.
It may have a 2.41 or 2.56 rear axle and/or single exhaust with highly restrictive muffler. Might also want to check ignition timing advance and carburetor operation.
before you do anything, get an oil pressure gauge and make sure the pump isn’t worn out/low oil pressure. If so, replace the cover and pump.
Block the exhaust gas cross over, rebuild and tune the Q-jet, recurve the distributor and set the initial with way more timing.
How much depends on your location, elevation, temps, and fuel. Duals, 2.5” mufflers, tails can be 2.25 with little loss.
The old school b1b intake is good, unless you want to keep the intake stock. 72 ditch the points.
beyond that…in a heavy B-body, you need some 3.42s for the 9-3/8.