A 360 is a tight fit, even in a 87, so you can imagine a 440 is too, esp in a 03. is it 4x4? May need custom headers or weld your own. Hopefully you have mocked the block up already with the frame, power steering, crossmembers, because headers are the least of your problems.
My opinion is that a hot 5.7/6.1 would run circles around that 440, with a whole lot less headaches (ie $$$$ and time)
A 2003 Dakota has nothing in common with the older 87 to 96 Dakota other than the name.
Pretty much everything is different, the frame is completely different.
I believe that there's someone here on Moparts that has a big block 97-03 Dakota (a blue 98 IIRC).
A Gen 3 Hemi would probably be an easier fit, but unless the original poster already has one will cost more to do the swap.