Re: carb swap?
The 33hp carburetor has adjustable needles, high and low speed. The 40hp carb has an adjustable low speed needle and a fixed high speed jet. So, if you put the 33 carb on the 40hp motor, you will have to adjust both needles. In a way, that constitutes "re-jetting". If you were attempting a swap the other way, 40hp carb on a 33hp motor, you might have a problem with the fixed jet size.
You MAY lose a bit of performance, IF the 33hp venturi (the bore through the center) is smaller. I don't know if it is or not, but you can tell by a side by side looksee. However, even if it is smaller, I doubt you will be able to tell the performance difference.