Like I said there is a very small chance that the transmissions are the same bell housing. But there is no way that a 2.5L is a 60 degree motor.
60 degree means that the cylinder banks are lined up 60 degrees apart.
The 4.3L has them lined up 90 degrees apart so it can be called a 90 degree motor
And since the 2.5L is an inline engine the 1 bank is lined right up
If you get a parts truck for the swap make sure that it has a good transmission in it, then your set either way.
If it's a standard transmission Advance Adaptors makes a bell housing for a v-6 or V-8 swap, although they don't recomend it due to the transmissions being weak.
http://www.advanceadapters.com/catalog/037.html