489,741 or 742, the Difference?

I have a 69 Barracuda with the original 7 1/4 rearend that I want to get rid of. I also have an 8 3/4 housing and axles without the center section. When I see center sections offered for sale they state different casings such as 489, 741 or 742.

What center section should my A-Body have in it? Does it matter?