The first combination we ran in "Walter" was an open rear end from a full size '78 Blazer with 3.08 gears and a Saginaw 4 speed. Our Saginaw was a 3 groove so it had the 3.5 first gear but the 2 groove with the 3.11 first is probably better with closer gear spacing. We ran 235/70 15 rear tires and it was a great combination with the 261 engine. We chose the '78 Blazer because the width was almost perfect and it had 6 lug axles so we could keep matching rims front to rear. As Ghostrider said, you'll have to relocate your spring pads.

1964 Chevrolet C-20 Fleetside, Otis
1950 Chevy 1/2-Ton, Kirby
1950 Chevy 1/2-Ton Shortbed, Walter