If you Order a New Perazzi via a dealer wih specifics regrding the stock he can usually do two things if he chooses. Request the specific stock dimensions you want and/or request an upgrade. There may be a specific stock that fits, in inventory.
The custom upgrade will cost you unless it is from a gun dealer that travels to Italy and will go back and pick from the Grade I's.
Virtually all Perazzi's, I have learned, are 'custom' in the way orders are treated - more like a well tooled job shop. It will take longer unless your dealer is a strong one.
Also - if you order a custom stock thatdid not leave the factory with your iron, fit it properly. Do not assume you can just crank it on..
I understand that Perazzi offers a complete custom dimension stock included in the normal purchase price of any new Perazzi.
I was measured and fitted for one while at the Spring Grand in Tucson a few weeks ago, but have not finalized the order.
Since then, some have told me that the Perazzi wood will not be of very high grade regardless of price and that there are some custom stock makers, e.g., Wenig's, which will make a much nicer and better fitting stock than Perazzi.
Have no personal experience with either's finished custom stock.
Will have the Wenig people measure and fit me while at the Southern Grand this coming week.
Don't know which way I may end up going on the stock.
Consider that whatever discount they'll give you will be no greater, and will likely be considerably less than, their cost. This means you will likely be able to sell the wood for more than you will save.
Order your Perazzi with stock dimensions that are "neutral", meaning that if you took off the butt stock, you can sell it really easily to anyone without them making much modification to put it to fit them. Take whatever money you get from selling your stock and it towards a new stock from a custom stock maker. That's how I would do it.
As zzt says, there is no guarantee that Perazzi Italy will make your stock to your correct dimensions. They sometimes screw up.