There is no difference between a 2wd and a 4wd frame. I converted a '59 3200 to 4wd in my driveway several years ago with no help. I used a NAPCO front axle and transfer case, which are direct bolt on components. NAPCO advertised that the owner could convert his truck to 4wd in about 3 hours... it took me about 3 days, but I used low-tech tools and took my time. The conversion is as easy as falling off a log. I spent today working on converting my 1950 2 ton truck to a NAPCO 4wd. It's the same process, but everything is heavier!
Task Force frames are completely different than the 60's model trucks, so a direct bolt on ain't happening. Most people shorten, or lengthen a 70's Blazer chassis if they don't care about originality.
If you have any questions let me know and I'll help you figure it out.
Take care, George