24-fret board on a Fender spec P-bass body
absolute was of $$$ IMO as you won't be able to reach those extra frets without a little left hand gymnastics. if it was a custom body, it'd be a different thing because you would design to compensate for the access to the added range.
there's a big difference between what can physically be done and what is worthwhile of being done
a Mahogany body sounds nice with a Dark Star ... but don't brush off the great sound of Alder or Ash as a good choice as well.
all the best,
R