Np435 into a 1984 gmc 3500

The GM NP 435 is sort of a rare and odd one .... or two. They apparently made 2 different versions a NP435A and NP435D.
I don't believe you can, because the GM version of the NP 435A had different gear ratios than the Ford and Dodge versions.
And I believe both GM versions had a roller bearing input, not a tapered bearing input like Ford and Dodge (except early ones).

So, I guess you should probably figure out which version and ratios that your Dodge NP435 has and input bearing before going any further.

More info here.

Yes you can swap the 205 input and adapter(s) to the dodge.

I have a dodge 205 adapter and coupler but you will still need a dodge 23s input