Advice needed

[motolover]

so i am a complete newbie when it comes to rear ends, i have a 66 c10 with a 454 and a th400 tranny the only modifications to the motor are headers, edelbrock 750cfm carb and a edelbrock rpm air gap intake. i have a 12 bolt rear end that i am going to be putting in the truck but it has 2.56 gears. will that work for my application? i am also thinking about going posi but i have no idea where to start. any advice is appreciated.