Stock magnum max lift

Around .470 iirr *with stock type seals.
Positive seals will allow more, probably the .500 you see with the crate mag.

As far as I know the stock springs are 80lbs seat and near 200lbs [email protected]
Weak, but you have to remember the engines intended rpm range is idle to 4000 rpm. The intake is focused on ram effect,long ram.. so again the 'sonic pulses/signal' if you will..have to go the length and back ..so the longer it takes, again..low rpm.
The 413 long rams were the same idea, and that motor was not a 6500 rpm power house. They typically petered around 5000rpm.

The seal clearance is the issue with more lift beyond .470 , then the increased rpm makes the springs an issue from there out.