exhaust pipe sizes

I have 95' 4.3L and Im trying to put a magnaflow on it instead of the stock, I'm wondering if anybody knows the size of the pipe that comes from the flange,  to a stock muffler? (outer diameter a preference) because Im going to have to use that piece inorder for it to work.  
 
thanks

on the stock exhaust that I had on my 2000, the pipe from the cat to the muffler was 3'' and from the muffler to exit was 2 1/4''.  I recommend a 3'' from the cat to muffler, and 2 1/5 to exit. I also think that magnaflow is not a great exhaust and Flowmaster 40's perform better and sound better compared against the magnaflow cat back system. 

Thanks for the help Im gonna try it out this week, Yeah I checked the sound clips on some other posts(wasnt too impressed with the magnaflow, but a friend of mine got new exhaust and the stock one i have on is just about shot) so Im not really looking for sound  just a functional muffler