I have a 2001 Chevy with a 408 that should push around 600 HP at the crank. I need to replace a fuel pump so which one and what size should I go with? Thinking of boost in the future to push it to 750 or more at the crank. Looking for an easy upgrade so an install kit, etc would be nice.

A walbro 450 would meet your needs.

Would that be this one:
http://www.summitracing.com/parts/vpn-f90000267

Also, is there any other things I need. Wiring harness, etc?

You will need to upgrade the wiring for the 450. You will also need an aftermarket fuel pressure regulator since the 450 will overpower the stock one and leave you with overly high and uncontrollable fuel pressure.

Will I need a new regulator for a 322 pump? At what fuel pump level do I need to upgrade the wiring? How much wiring has to be upgraded?