See if you are in etis http://www.etis.ford.com/
The list of features includes the Sync version:
Primary Features
Build Date: 31.05.2016
Vehicle Line: Mustang
Body Style: Coupe
Version: GT
Engine: MOD 5.0L-4V DOHC SEFI NA
Transmission: 6 Speed Manual Transmission-MT82...
I think Davo is away at the moment but from my checking (first timer at this)
TAMESIS:
Booking Ref_____num____Dest
USBAL1446247_____1____BRI
USBAL1446248_____2____FRE
USBAL1446249____12____PK
USBAL1446250____16____MEL
USBAL1446758_____1____PK
USBAL1446759_____1____BRI
USBAL1446760_____3____FRE...
There is a small difference, maybe 1mm or less but the tread depth across the tyre is slightly graduated on both tyre sizes.
Fit is good (rear rims are 11") and I think they look the business!
I have some coming from the USA tomorrow MRR GT350 rims with 275 front and 305 rear Michelin PSS. Ordered thru Need 4 Speed - reasonable price even after duty/GST and like you say got the 305s. I wanted to try a set (why not) but dont know what will happen when I need to replace them.
Cheers
Titan Ford in Brookvale have a Comp Orange GT auto with over the top stripes - same as my one on order (apart from the auto) so we went and sat in it for about an hour on Saturday (oops). Felt good though.