vl Rb30 class rules state rear end must be standard,it refer's to the differential or to the chassis's inner/outer wheel arhes?

What class? Only VL classes i've heard of are imaginative things created here

I assume you're going off the fullboost records as that's who made up the VL class. usually guard modifications are fine - they're usually referring to suspension and chassis configuration when they refer to 'standard' configuration.

It refers to the chassis rails does it not? Mini tubs and differential upgrades are allowed because the standard chassis rails haven't been touched.

hi, i'm only new here and doing some searching and found on the tool bar's far right hand side a "dragracing" page. in there is different classes for the vl commodore. My question was about the diff, To be more specific, can the original diff be shorted and still be in the street class?

yes it can what you are rerfering to is original location points of controll arms shocks springs etc you can box your trailing arms wich is recomended and roll guards im not 100% sure on if you can fit flares though om pretty sure if you wonted to you could cut and square your inner wheel wells ? however shorting the diff you will only get and extra 5 mm from each side so the cost is not realy worth it in my view considering how quick the stock wheel sized guys are going