Re: Which Head and Cam combo??
Chris is a very good engine builder, and he is still making motors for sale to customers (I am not). He and I agree most of the time, but he generally likes to add about five more degrees of duration than I like for a street driven engine, and he favors a shorter lobe separation angle which builds more peak power, but it also lowers manifold vacuum due to the increased duration.
Basically duration is added to an engine build if you favor higher engine RPM's because it gives the engine the time it needs to suck in the air required to combust the fuel. Everything about building power in an internal combustion motor is all about getting as much air in as you can (which explains why blowers are so popular). Since air is a fluid it follows loosely most of the rules that are spelled out in the laws of fluid dynamic (mostly Bernoulli's equation, that others have added modifiers to over the years). Because air is compressible it doesn't follow all of the laws exactly but closely enough.
Like any fluid it takes time to get from a to b. It speeds up in an restricted channel and slows down in a broad one. Because of this there are as many people that swear by one head over another. the difference is in how they have put their engine together. At high RPM and larger displacement you need a larger port, slow down the air speed such as occurs on the street and you want a smaller port. It is about maintaining the flow velocity in the port all the way to the valve that determines the amount of power you will make.
That is why no one uses a rectangular port head (unless you have at least a 502 (540 is a better) minimum size but requires a 4.500 inch bore block which leaves a lot of 454 4.250 dia. bore blocks wanting), or have a car that lives on a trailer and is shifted at 7,500 RPM. By the way you are creating a huge weir in your port that will cause all kinds of havoc with air flow using that manifold with oval port heads (You need another intake manifold). Compare the price of rectangular port heads on e-Bay to oval port to illustrate how popular rectangular heads are today.
Brodix or AFR? You are not comparing apples to apples. Brodix and Dart include in their instruction sheet information telling you how thick and where in the port you are likely to hit water. This is because they fully expect you to port these heads to match your engines final needs. AFR is used right out of the box as is, and they state that you will ruin the head if you attempt to port or polish it. Trick Flo has recently discovered Chevys of late and has been making better heads than before if you believe the car rags. I am not going to even talk about buying off shore copies of other manufactures head designs, as you get what you pay for, and they are usually inferior in every way.
They were mostly Ford guys before, as Indy is to Chrysler and MTS is to Cadillac. Edelbrock is the Chevy of aftermarket heads. Entry level, and with a little work in bigger valves and stiffer springs, are probably the most bang for the buck. Which is why I ordered my Edelbrock heads bare and added bigger Manley valves and PAC springs. They also have quality good enough to meet GM's OEM requirements; and are used by GMPP for all of their aluminum manifolds and heads used on crate engines. Edelbrock has also been renting time on universities super computers to redesign their heads for wet flow. They did this earlier with their intake manifolds to noted success.