is between 4500-and 5000 the best shift point?
Other than chest beating that is what dynos are for, to show you where your power peaks are for shifting.
To answer the redline question...two things will limit your RPMs.
1. Valvetrain. Your cam/lifters/rockers/springs can only go so far so fast. Once you reach their limit your power will drop so far that you CANNOT rev any higher.
2. Bottom end. Your crank/rods/mains/bearings and their various connectors can only go so far so fast before they begin to lose stability and cause the oil pan to fail.
On my car I had the short block overbuilt for my purposes and the blueprinter (DSS Racing) said my bottom end was good to 8,000RPM due to oversized rods, mains, and connectors (plus the girdle). Then I chose a camshaft that will basically give up at 6,250-6,500. Doing that keeps things fairly safe if you ask me.