Depends, on where you are going to install them.
XL Joints 1350 outside clip style: 3.622 width with a 1.188 dia cap.
XL Joints 1410 outside clip style: 4.188 width with a 1.188 dia cap.
XL Joints 1480 outside clip style: 4.188 width with a 1.375 dia cap.

The input and rear output on your NP201 are 1410 outside clip joints.
Your front and rear axles, front NP201 output and NP435 output are all inside clip joints which use a Detroit style 5380 or a Moog 304.
These are 3" wide inside clip and use a 1.230 dia. cap.

So, in my opinion to go to the 1410 or 1350 series XL joints you are talking some serious money to have all new ends put on your shafts and new yokes too.
I really don't see how you could just modify what you have? The input and rear output on your NP201 is already a 1410, which will work, but everything else is not.
Just measure your joints and verify whether there inside clip or outside...............

Mark D.

1968 W200 Sweptline
1969 D100 Utiline
1971 D100 SE Sweptline
1993 D250 Club Cab Sweptline
1986 W250 Cab & Chassis
1978 D300 Sweptline

E. Brookfield, Massachusetts