The lug pattern is the same but the 2003 has a larger disk brake needing a 17" rim so a 16" rim off a 2001 will not fit. However you could put the 03 rims on the 01.
No, the common rail fuel system started on the 2003 model year Dodge.
12
On a 2003 Dodge Cummins truck with a HO engine is rated at 305hp, with the SO engine it is 250hp. BTW there is no "g" in Cummins. ;)
No.
Yes
No.
The wheels off a 2003 will bolt to a 2001 with no modifications provided they are the same series of truck. (1500 or 2500) if they have the same number or studs they will fit although you may need different lug nuts depending on the style of wheels and nuts they each use
Doesn't have one.
7 gallons
No, the offset is wrong.
One from the factory.
The 2003 has an electronic lift pump. The system is self priming if the lift pump is working.