Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
New CPU tray

May be better to buy new 5,1 machine.

At least be glad it isn't held together with Security screws, you can upgrade what you like.
 
You can certainly put in a single 6x3.33 easily but if you want to go to the twin-cpu for a dual 6x3.33 then yes, you need a new CPU tray with the heatsinks.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.