Gday mate im gonna be undertaking this exact task in my wh grange. Ive got nearly everything I need just a few bits and pieces left. First and foremost yes the dash will get fit. Best part is the heaterbox is the same. But your gonna have to get your hands on a complete body loom from a wk caprice. I say caprice because then its got everything. Youll also need a bcm and keyhead to suit as theyre different, both electric seat looms if your keeping the wh seats, door looms, vy/wk fuel sender, roof loom (sunroof/no roof, caprice roof accessories etc not needed if you dont want them), passenger airbag, youll have to splice the boot lid loom into the wk one so you have reverse lights and obviously every switch and button including the cluster. Everything must be from s wk as wl have the alloytec v6 and 6l v8 and as such are completely different. Now if it weren't for the bcm you could literally just repin the new wk accessories to the original wh loom. I know this works as ive done it already for the roof and ive compared the 2 looms at each plug and can confirm there identical and its just the plastic connector that's different. This all sounds very daunting I know but honestly once you've stripped out your interior and removed the original loom, putting the new one in is a bit tedious but after all the looms are put in place and if your careful enough have retained the mounting clips, putting everything back in is literally plug n play and itll be done before you know it.
Finally the price. ..start saving bud, the loom from a wreckers including the bcm and keyhead is gonna cost around $800 and I bought holdens last one ($350). I also managed to keep my luck going cause I picked up everything accept seats (ive got ve senator signature front seats to goin) for $150... hpw and other wreckers charge more than that just for a cluster or the centre console overlay... any questions feel free to ask