I'm wanting to put a lightning or a svt mustang powertrain in my 51 I can get a motor tranny but are unsure if I'm gonna need the stock ECM or would a stand alone be a better option any input would be super thanks

 

I would go mustang, much larger parts base to work from. not only that you wouldnt have been the first person to do it. The ecu choice is in my mind is broken down into whether or not you are going to run a auto or stick tranny. Stick i would go stand alone, potentially more easy to tune depending on witch one you get.