1968 Road Runner '383' vs. 1968 Chevelle 'SS 396'
Magnum Dart
On the 1968 Chevelle SS396 'L-35'
If you measure horizontally, the 'Amber' does start at 5200 RPM's like you stated.
And the Red-Line, looks to be just a 'tad' under 5500 RPM's.
http://chevellestuff.net/1968/images/68_5500_tach.jpg