need help with my rear end (no pun intended)

[Budman56]

I want to change the rear end in my 65 c20 chevy truck. my truck has trailing arms. I have rebuilt my 327 motor, and converted over to a 700r4 trans. so I have been told to change the rear end, but I dont know where to start. so I need to know what year car or truck rear end would work? how do I tell what gear ratio it has? and what should I look at spending to do this change?

any help would be greatly appreciated!!!!!