OK cool!
Limitations not in compression or how well they port out. But yes. Limitations in compression and how well they port out as well as how stable the valve train is and it's max lift is.
OK, I think I may have confused you there.
The stock, as delivered head can only accept so much lift. What lift I don't know and how far it can go is up to the valve, spring and machine work by the machinist. This issue is with all stock, as delivered heads.
They have rocker stability issues. (High lift and RPM) There fix is a girdle, just like a Chevy. You can even use Chevy rocker arms in a Magnum head.
Porting. All heads have limitations on there metal available to port out. The Magnum head does OK on porting. The more you can port the head (for more air flow) the more power you can make.
Do a comparison of ported heads.
Compression is not an issue. But fuel is. That is if you don't want to run E85 but just gasoline in the street. The small chamber helps make high compression.
You build the engine with a desired ratio. How close you get to that is your choice in the challenge.
Yes and no.
How fast do you want to go?
Very fast? Will stock heads get you there? Probably not.
As far as actual "Magnum" heads and gear goes, as far as I know, there are only 2 heads currently being made that are "Magnum" heads.
W5 & W2. Oil through pushrod LA heads on the Magnum block.
There are a couple of guys running all Magnum engines. And a few good magazine write ups.
What is your goal? E.T. or dynoed HP number? What car are you using? Is it track only? % of street & track?
With some of the posted/listed flow rates of ported Edelbrock Magnum styled heads, making 600 NA or better HP is possible by the numbers. If your car is a dedicated track car, a severe car lightening program can have the car running quite quick.