Besides the sound, you’ll see limited benefit from raising the rev-limiter too much beyond 7000 without going to a built motor with serious head-work.
You’ll see valve float (valves losing contact with cams/buckets) at some point, which is all kinds of bad. It sounds like you’ll see around 7500, (as stated above). It’s good to leave a bit of margin there. Usually float happens before your rods decide they want to leave your engine, but that’s a consideration too.
Practically speaking, you’re limited by all the same things an all-motor build requires at higher RPM - cam duration and head port flow being too brief to let enough air in, valve diameter too small, intake and exhaust manifold runner lengths too long, etc.
Even if you get a monster big turbo that will flow enough at higher RPM without running out of breath, it’s generally so much more effective in a turbo motor to just turn up the boost wick to get more power, especially since factory turbo engines are designed to flow at lower RPM ranges with a broader powerband - exactly the opposite of of a peaky high RPM motor, so you’re fighting a lot of OEM design decisions.