99% of the time the part #'s will work out like this..
40 series = 2 chamber muffler
will start out with a #42 followed by 44xx( the xx's are more #'s of diff. types of mufflers) or 54xx so it would be like 4244xx
you may find one with starting with 43.
40 series Delta= 2 chamber
same thing but they start with # 94 and have either 24,25 or 30. example 9424xx
50 series Delta= 3 chamber
#84 with 25 or 30
super 40 = 2 chamber
#95 with 24, 25 or 30
so try and find a part number starting with one of these that has some of the other #'s and that should tell you what muffler you have, other than that this is the best I got for you.