Well, that sounds unrelated to the rearend issues. There could be many sources of those smells...
Coolant could be coming from cracked intake (very common issue on 96-01 Mustangs and other 4.6l), over-filled overflow tank dumping excess coolant, overheating causing coolant to boil over, pin hole in radiator, leaking hose, leaking intake manifold gasket or water pump gasket, bad water pump...
Is it loosing a noticeable amount of coolant? Can you tell where it's going? The first places to look for coolant is in the block valley, spark plug holes and on the front of the block and oil pan. If it's a small leak, it can be hard to find sometimes though - a few drops of burned off coolant can really stink things up.
Oil smell is under the hood and not in the exhaust, right? Any visible smoke under the hood when you smell the oil? If so, see if you can trace it to the source. The PCV system is the first place I'd look - when's the last time the valve was replaced? Make sure the hoses are all in good shape - no rotting or cracking. While running, look for oil dripping from a valve cover gasket.