The 390 mustang will run 14.50s in the quarter, stock, Thatís what mine did any way. A 428 SCJ cam, 750 Holley, and 3.91 gears and it ran 13.50s.
Putting a 428 crank in a 390 is a little more complicated than just putting the crank in, The stroke is longer so the rods and pistons will also need to be replaced. And 428 cap screws for the rods, or the 390 type nuts will hit the block, and when replacing a crank the rotating assembly has to be balanced with the harmonic balancer and the flywheel.
The 390 looks great and sounds great, It's also heavy and gets baaaaad gas mileage, and wont make any more hp than a 302/351, The parts are hard to find and expensive for a 390 compared to a 302/351.
In the end it's up to you.