I will put my too bobs worth in to help out.
I actually do exactly what rusty states but to get the mufler back into the block I use a rubber mallet and tap the top of the muffler lightly by guiding it back into position. If your worried about the muffler place a small piece of wood in between.
If you tap the front of the muffler it wont go back into position.
the trick is to always put the bottom clip on first.
I then use a small piece of thin scrap metal to prise the top clip into position. I havent had a problem following this method.
