There's is all the info you need in a topic from 2014 titled brake pad retaining pins.
It depends whether you gave solid or vented discs.
From memory vented pins are 86mm long and the springs 56mm wide - solid discs pins and springs are obviously shorter / narrower.
The vented pins / springs are nigh on impossible to find these days, and only from Vauxhall (If still available).
thanks mate ill pull a wheel and check
2.6/3.2 left the factory with vented rears. Everything else had solids. No ifs. No buts.
Vented callipers have an 8mm filler strip between the two halves and 42 stamped on the outer face (this refers to the 42mm pistons as opposed to 40mm of solids.
Fitting solid discs to vented callipers WILL almost certainly result in death. YHBW.
Oh, btw, parts guides/Mintex/Apec claim that the correct size fittings for Omega vented rears exist. They lie. You can waste £30 finding out for yourself if you like.
Also replacement vented callipers aren't available. Solids however are. This gives you two distinct choices:
1. Buy the correct fittings from VX, £45 last time I got any and fit with vented discs, as per factory spec.
2. Buy non vented callipers and use readily available solid fittings along with solid discs.