Fox Planning on 5 lug swap -which axle ?

You can just stick the 94-98 axle shafts, and brake hardware from any 94-04 Mustang on your current rear. All 86-98 housings are the same, so no need to buy an entire axle if yours is fine and you've invested time/money into new ring gear and rebuild t-lok and such.

The 94-98 axles come out about 0.75" wider each side than stock fox offset. You generally want a BS of around 6.25-6.5" to get a 9" wheel to sit right with those axles.

Or, buy the relocation brackets, and 5-lug fox axles with SN95 flanges from LMR and have a stock fox track out back. Then you have way more options.

Usually I suggest running the sn95 94-98 axles if guys are committed to running SN95 17x8 wheels all around (of aftermarket wheels with the correct deeper offset). They fit perfectly out back. Anything else....fox length is the way to go.

I might just not a fan of spacers. I know guys run them without issue but I prefer to avoid.

17x8 sn95 wheels on fox axles without spacers looks odd