20" Wheels for a 1965 C-10--Info needed

[4shongo]

I just bought a 1965 C-10 with a service bed and want to put on some 20" wheels (6 lug); maybe Boss 338 (gray with polished lip). Tires; 275/45 in the rear and 255/55 in the front. I have been searching and cant find many pics of 60-66 trucks with 20" wheels plus info (size, width, tire used, any issues, etc.!). Any info would be appreciated. What worked? What didn't? Will wheels from new model GM trucks fit? I plan on doing a mild 3"-4" drop. Thanks guys