hey rocket man!

i asked same question a few weeks ago, came to the conclusion its best to run through the cab to prevent any damage occuring plus it looks neater :)

i have a ca18det, i ran the cable through the firwall, then under the carpet on drivers side, through the back cabin wall and then outsideand up into the tray... i wholesawed 3 new holes.. i recommend using some beefy cable to prevent any volt drop etc..

its recommened u use a smaller size negative to run to the engine block anyway,somewhere near started motor and also run a recent size to the body, make sure the paint is bare etc and have a solid connection... once tight put a lil bit of paint over it to prevent rust too :)