Honestly I feel you would be better with finding a four speed, in a donor truck, so you/shop can swap all the parts over as needed.
With that said, a nv4500 is nice with overdrive, hence more costly and some shops may not want to do it.
C20 2 wheel drive may require new driveshaft for either swap another 3-400 on top of say 2500 to do just manual swap