Power and rev limiter

[blankczechbook]

if wheel output was accurate then all sounds ok for std cams.

losses do look big, so either you have big losses or you don't - rolling road details might highlight this issue.

if there are lumpy cams then you'd have slow idle issues on std dizzy/carbs perhaps ??

6000 shouldn't be too low - you shouldn't be bogging down - you haven't mentioned this.. so it doesn't sound to be the cause of your lack of ummph.

if it is otherwise OK, WOT is available - pulling cleanly through the range and plug colours look good - then look to weight savings / flywheels / rims + tyres etc etc..  - before other cams/engines. IMO