Radiator

You won't need a performance radiator unless you're tuning the car,
and generating more heat in the motor that needs cooled more
efficiently. The radiator is the same for the V6 and V8, the
performance just indicated it's less restrictive and provides more
volume.

This rad says is for both V6 and V8, not performance:

Note the upper and lower rad connection points.

This one says performance, GT:

Not the upper and lower hose connections; they're in the same spots, so why can't
you use it?

There are two different EcoBoost rads, I am guessing you mean the GT350 ecoboost
rad?

If you check the fitment data for these rads, it still says V6 Coupe 2-Door,
3.7L 3726CC 227Cu. In. V6 GAS DOHC Naturally Aspirated.

 

Just get with your local Speed Shop lots of people make good radiators

 

After looking on the Ford Parts web site, the V6 and GT share the 'same' part number for the radiator. I have 'never read' about 'overheating' problems because of the radiator being too small on the 2011+ Mustangs, GT or V6.

I wouldn't mess with something that doesn't need messing with

 

If you buy the OE V8 Rad, it being the same as the V6 Rad, won't void the warranty.

You'll probably have to go aftermarket, and compare the thickness and number of
fins per inch -vs- OE, and then if you want plastic side tanks, or aluminum...
More then likely, you're going aftermarket:

Aluminum Side Tanks
52mm, 3-Row core
129% (+77% over Performance Rad) increase in coolant capacity over the stock radiator
26% increase in coolant surface area (tubes) over the stock performance package radiator
55% increase in air surface area (fins) over the stock performance package radiator

Core Length: 25.4"
Core Height: 19.9"
Core Thickness: 2.05"

25.4 x 19.9 x 2.01, compare that with your stock rad: 25.25 x 14.38 x 1.44 in.

Here is a Side-by-Side:


eBay...

 

You are welcome.