T-Lock
 

where can i get one and about how much should it run me?

ebay has them, and you can get them from $50 for used ones to $200 for brand new ones.

so i would want for my 7.5" rear end correct?? would this one or one similar to this work?? and is there anythiing else i would need with it or what>?

http://cgi.ebay.com/ebaymotors/ford-...spagenameZWDVW

Get gears while your at it. Save on labor.

Yeah 7.5" 28 spline is the way to go, maybe some new bearings, just get an install kit from MustangTuning or (AmericanMuscle). And gears should be put in at the same time, 3:73 or 4:10. About 250 for labor is normal.

all you need is the install kit which is very cheap. But you might wanna ask how many miles are on it so you know if its in good shape or not. if its not you need a clutch pack rebuild kit whihc are 35-40bucks.