I am pretty sure this will work, but just want verification......

I am thinking of buying a 2003 F-150 with a 4.2 V6 that the owner says does not get over 35mph and needs a new transmission.

I have our sons 'old' 2000 Mustang that through a rod and has been sitting in our driveway for a couple of years now.

AFAIK, these both have the 4R70W transmissions, and neither are modular engines, so it should bolt in.
Electronics are the same (right?), and I presume the linkage and driveshaft from the F-150 will bolt on to the transmission without any issues.

Anything I need to be concerned about?

Lastly, I am presuming that the reason the truck won't go over 35mph is that it is not shifting past 1st or 2nd gear.

Thanks for any comments and ideas.