408 vs 600 stroker

You do not need nor do they make all aluminum internals. The crank will be steel and the aluminum rods would not be a great choice. The 440 block will break long befor the use of a good power adder can be fully used. Thw small block may be a better option. Anything over 800 on a stock rb block will require an aftermarket block and that is when the slippery money slope starts and your bench racing should leave here and become you giving a LARGE sum of money to a good builder.
this is not hate. If I had 20k+to invest I would not base my build off a forum thread no matter how knollageble some of the people here may be. (no knock against anyone here.