Dear Camel-
The cylinder heads that you are refering to, are correctly referred to as "Camel Hump" heads.
Yes these are good cylinder heads for their time in history. They were closed chamber heads, meaning the combustion chamber around the Valve Pit is extremely small for high compression engines.
This was and is a good thing if you are going to insist on running cast iron cylinder heads. However, in all honesty, when I think about building performance engines, I am looking to loose as much weight as possible from the vehicle undergoing its diet.
In the day the cylinder heads were normally used on performance cars, such as Camaro, and Corvette. They also appeared on Yenko Chevelles, El Caminos, and Novas. These were installed on the COPO cars of the late 60's and early 70's until the emissions requirments were imposed by the Federal Government under pressure from your local Green "Pieces".
They are good strong cylinder heads, but if you are looking to build a nice stout Street Rod, you might consider selling them at a swap meet, to a rivet counter that wants to "Restore" a vehicle to its origional configuration.
For the record that is not my idea of a Muscle Car, but whatever.
Keep in mind they came from an era where you could purchase 100+ octain from the pump, and high compression ratios, with minimal emissions requirements.
Personally, your little 283, is a very good engine that has lots of room for good horsepower. There is many-a-289 in mustangs that produce 300+ horsepower without adding turbo, Nox, superchargers, or blowers.
In fact the current project that I am working on is a 1965 Mustang Fast-Back 4-Speed that came with a 289. We had the block bored .60 over, and it now has a forged steel crank. Its now a 302 as far as the CID is concerned, but the block numbers still state its a 289. When we ran the numbers, the engine dynoed at 375.6 horses.
That involved a cam, Eidelbrock EFI intake system, Performer Cylinder Heads, and some other goodies. This engine does not have Nox, or any other external add on pressure systems. Just a good solid engine, with the power built in by the parts you use.
So having said all of this, yeah the heads you have are a good start, but there are so many better products out there, that they would serve better on a vehicle that was being actually restored, not altered into a Road Terror. He He He :)
I hope that helps you out. Just for the record, Chevrolet has a book that is called "Chevrolet By The Numbers." It is a series that covers the muscle car era in the 60's and 70's. In these books it has listings of the cylinder head numbers. If you look up the numbers, it will tell you whether they came from a truck, (4-bolt main shaft) or a car, (2-bolt main shaft).
Good Luck!