The 60s are fine, its your tune. Wasting your money downgrading the injectors and if those 39s are secondhand from a Cobra you shouldn't be running them on a 2V. If they aren't then disregard.
And as was said, that canned tune you bought is not going to be a good idea, you need a dyno tune and it will run great.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.