Their are no direct bolt in 9in rear ends. Your factory 10 or 12 bolt is 64in wide from wheel mount surface to wheel mount surface. You will need to find one close to that wide unless you are going to tub or mini tub the truck. You will have to remove all the mounting brackets off of the 9in and instal new spring perches and reuse your old shock mounts. Ford truck 9in have 5.5in bolt circle and even some later models have a 4.5in bolt circle. Most car 9in rear ends have a 4.5in bolt circle but the Ford Thunderbird and the Lincoln Continental from the 70's have a 5in bolt circle.
The only way you might be able to get a direct bolt in would probably be Currie Enterprises in CA, they can build a 9in to your specs. They might have the specs on a c10 but I dont know for sure.
The best way to do this is to find a rear end, take it to a rear end performance shop, have them build it to your specs with new gears, carrier, axles, and brakes. Then when you get ut home you set the rear in place and weld in your mounting hardware, run your brake lines, and measure for drive shaft. It will he pricey but it will be right.
The cheap way to do it is to search till you lose you mind for close to what you want and just make it fit.
