I'm gunna convert the np203 to part time, will the mile marker 423 hubs convert the front axle to manual hubs or do I have to use other ones?
I plane on using the milemarker shaft replacement kit. also does the shifter assembly have an adjustment itself or is there another shift setup? I have adjusted several times and is better but it will not hold the one lever engaged.

here's the procedure for adjusting the np203 levers:

It's not that hard - Put the tcase in neutral, make sure it's in neutral, undo the shifter linkages(back off the nuts on both sides). There is a hole in the side of the shifter & both levers, move the levers until you can put a drill bit (if I remember correct it's like 3/16")through the hole & both levers, then tighten the linkages to that spot.
That re-sets the shifter linkages & the case to neutral.
The case might not be in neutral when the shifter says it is, you have to make sure the case is in neutral, otherwise it will be wrong.