Re: Rectangle intake with oval heads
As mentioned the motor will run. I addressed this issue the other day with a 8-71 blower manifold a guy wanted to install for looks. Performance wasn't as important as display as it was built to cruise car shows.
The velocity people are talking about is the velocity of the air in the runners. When the 427 Mark IV went into production, it was based upon the designs of the Mark II big block that was built in 1963 to compete in NASCAR. NASCAR is all about WOT. They do not normally spend much time rowing through gears from stop light to stop light.
Because of this the engineers were looking to optimize laminar flow for peak horse power. That is why the intake was taller than similar Rochester 4G carbs, with straighter shorter length ports. Now I do not know how much time you spend holding the accelerator pedal on the floor, but in Florida such behavior will probably come to the attention of the local constabulary.
For that reason and probably to keep those party poopers in California happy (the originators of the smog police) Chevrolet also introduced the "large port" round heads you have. Racers learned over time that the 350 horse 396 actually ran better than the 375 HiPer version on the street. Especially when given a high lift cam similar to the 375 horse cam.
It is generally now accepted that anything less than 500 cubic inches is best served with oval port heads because the smaller diameter of the ports really sends a strong vacuum signal to the carb to suck in more air. With 500 cubes the break point, Chevy ships their premium street engine ZZ502 (502 hp) with oval ports, but the lower rated 502HO (450 hp) with the larger rectangular ports on cast iron HiPer heads.
You can demonstrate this with soda straws. If you get a bunch of straws of varying diameters you will quickly see that on the jumbo red Slurpee straws from the Seven/11 can suck up a lot of water but you can hardly pull a vacuum with air. Conversely the little red swizzle stick from the coffee counter wont hardly let water pass but you can pull a "hard" vacuum with it. The red and yellow striped white MacDonald's straws are perfect for sucking up both air or water. This is a Three Bears demonstration of the physics principle of fluids based upon formula developed by Bernoulli.
Motors run on air not liquid gasoline. The amount of air that can be ingested by the engine determines your peak horse power. But it is the torque curve that allows you to live with the internal combustion engine on the street, and it is a compromise of peak air flow and cylinder filling with the correct ratio of air and gas. Bigger is not always better.
But in your case it is way cool at car shows so if that is what you want go for it. Just watch for vacuum leaks because of the port mismatch, and be prepared for a slight loss in power and throttle response.
Larger Dave (of I remember when fame)