I have a 2004 Dodge with a magna flow 15863 that
is rusted and going to crap... Should I put the same
thing back on or something else?
MagnaFlow is a good muffler and should last for at least 10 years. Is the rust just superficial and not eating holes in the muffler casing? In that case, just leave it alone. On the other hand, if the rust has caused the muffler to fail, look into FlowMaster or several other manufacturers of performance systems. Borla is good but expensive. Walker is good and relatively cheap.
It is rusting holes and causing exhaust leaks constantly