Advice on 275's up front?

with good quality tires and a good alignment and you won't see anymore "tracking" or tramlining with 275 on the front than any other low profile tire...it's short, stiff sidewalls that can be an issue

anyway, I've run 275/40x17 on the front for a little over 200K of my cars 250K miles and they work just fine
 
I have had mine done on a laser alignment machine and the front end parts are like new and mine still likes to wander. I think a lot of it is from how crappy our roads are here.

do you have C/C plates so you can get a reasonable amount of caster? 4.5*-5* of caster really helps the relatively primitive suspension on the Mustangs track a lot better

and frankly the 3/8"-3/4" extra width in the front tires is a lot less important than the quality and condition of the tires themselves