The NV3500 is considered a bit weak. You might consider the NV4500 as well. You'd need a 4x4 version and the NP205 you have won't bolt up unless its a late one w/ round input pattern The input is also 27 spline and that won't work with the NV4500. I can't speak to the NV3500. You should be able to get an adaptor to bolt to the NV4500.
Of course you need a bellhousing and clutch pedal, linkage and so on.
I think a 700R4 might be the easiest swap, but again, mating it to the TC could be an issue.
Try checking out Advance Adapters conversion guide.
The following search has a K10 swap TH350 to 700R4 link. You can do other searches as well.
https://www.google.com/search?q=k10+....0.269zFrHoYn8