I would start with a good tune and see how you like it. That will make a big difference and have you spinning your tires on the street with ease. VMP is a good choice.
A converter makes a huge difference but might be pricey for some. I ran a 4C in my 2011 which stalled to 3800 rpm. That with some supporting mods had me in the low 11's, on stock 3.15 gearing.
Stock converter stalls around 1800 rpm.
2015 Mustang GT Premium Sold
2011 Mustang GT Premium Sold
2003 Mach1 Sold
2.3 Whipple, fully built motor with all the bolt-ons 718 rwhp/735 rwtq Sold