I'm looking at picking up a rear end for my Challenger.  The number on the chunk appears to be  2881488.  Can anyone tell me what the difference is between this and a regular chunk with 489 stamped on it. From what I can research, this chunk was used in 69-74 in 8 3/4 applications.  Does the 488 perform as well as the 489?  Thanks for your time and help.  

I recommend you check the numbers or look for more on the casing.  I'm not an expert on them, but I've only read about 489 and 741 case numbers for the Mopar 8 3/4 rear ends.  

I'm with you Superbee.  741, 742 and 489.  This one is weird.  It also has a big 4 and an A circled stamped just above the number.  I did a parts number search and the 488 came up as an 8 3/4 rear with the same years.  I'm picking it up in a couple of days and I'll confirm the pics.  Thanks for your response.