'57 rearend?

[rsb5772]

Can someone tell me what the original rearend was in a '57 p/u? I'm not sure if the 10 bolt under mine was the original or not. I have a 10 bolt from a '73 Nova and a 9" with disc brakes, that I'm trying to find out what it's from, to try under my truck. I haven't measured the spring perch widths yet. Also, does anyone have any experience with a Powertrax Lock-Right? I'm thinking about putting one in the 10 bolt since it can be done w/o having to seperate the ring and pinion. Thanks.