There's quite a bit of difference between 2wd to 4wd frames, mainly the front cross member under the engine. They are riveted together from the factory & takes some work to convert.
I think the trans tunnel is also different from 2wd to 4wd. You'll need the 4wd tunnel & have to do some cutting/welding on your floor boards to to the swap.
You'd be better off in the long run buying a 4wd truck & sell your 2wd.
