IS there any physical difference between the La360 vs. magnum 5.9 Crankshaft???

I see your concern, but unless you're really turning up the wick, .020 or even .030 shouldn't be a problem as long as it's properly ground clearanced and installed. If you're that concerned about breaking a crank under boost, you really ought to step away from a stock crank, LA or otherwise, and go with a forging at which point, you could probably opt for zero balance.