when I had my 20/22 hybrid engine i rarely got over 6500 rpm but it did drop a valve at 7200 rpm once 
once was enough 
it depends on what cam you have what carb and what exhaust. if all are large enough it will spin up that high but it would have to be a VERY long and steep hill for it to over rev the engine. it just doesnt happen when you have dual cases and use them.
The engine build: Weber 32/36 w/adapter on a '77 intake(no EGR) port matched to cyl head, O/S int & ex valves(Engnbldr), Comp Cams 87-127-6(224* @.050" x .435" L), '83 cookie-cutter pistons in '83 tall block, LC Eng dual row chain & cam sprocket, Pacesetter headers 2" exhaust thru 2" cat & 2.25" series 40 Flowmaster.
I'll just have to learn my shift points by ear then
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