Stock Magnum heads

[1968fish]

How big of a lift cam can the stock valve springs handle?

 

[Bobzilla]

Stock Magnum valve springs are already inadequate for stock lift. Do not perform a camshaft swap without upgrading valve springs.

 

[dartfever]

Also can't go much over .500" lift or you will have guide contact issues.

 

[YY1]

I've read .520 is the number

 

[Bobzilla]

Post 18 in the thread below has my measurements from my engine. Some guys are running them with less than optimal clearance and getting away with it. I wanted make sure on mine.
Retainer to guide clearance will be an issue before piston to valve clearance, from what I am seeing on these.
How fast can you go with a Magnum? Who has the quickest setup?