I’m planning to make some upgrades to my Donzi 35 ZR this winter. The engines are being rebuilt and should dyno around 650 HP each once finished.

I’m trying to decide on the best outdrive setup for performance and reliability at that power level.

• What are my best options for drives?
  
• Has anyone here run a box extension on this hull? If so, was it worth it?
  
• How about shorties — do they make a noticeable difference in handling or top speed?
  

Any input or real-world experience would be greatly appreciated!

Don't have experience with boxes or shorties on that boat but you have options for drives which I have some experience with...

If you drive it well and throttle/come out of the hole easy, XR's will last for awhile

If you don't want to ever have to worry about drives again, get Imco SCX uppers with SC/XR lowers with 1 1/4" propshafts and drive it like you stole it. Putting a SCX upper on my boat was the BEST thing I ever did...one less thing to worry about.

Also again I don't have experience with those hulls but, if you run boxes and shorties you are opening yourself up to surfacing the props a lot easier and you better be good on the sticks if that's the case. Shock loading XR's like going in and out of the water is what kills them.