Need to buy tires front barracuda 1968 - w/ disc brakes conversion

A 215/65/15 will be 26" tall, which could cause issues with the front lower corner of the wheel opening. That's a pretty common issue with the Barracuda's the wheel opening is pretty tight. You'd honestly be better off with a 225/60/15, but it doesn't look like the Cobra's come in that size anymore.

What disk brake conversion do you have? The track width/backspace will make a difference.