9 inch open to lsd conversion

[cougarmanouverer]

I have a gradually increasing whirring sound coming from the rear end of my 69 cougar thats indicative of a wheel bearing. When i was under looking i found the tag of the diff which i found to be a 69 cougar 9 open diiferential with 3.00 ratio and a 28 spline axle. Is it as simple as replacing the guts of the diff with lsd gearing and how much would it cost?
The car is just a stock engine and only street driven with 295 tyres. What gear ration should i be looking for if i was to pursue this route.
The first thing ill be doing though is checking the bearings and axle before i went any further anyway

[gregaust]

You'd be best looking to a true trac, replaces the open centre .

Ratio , if u like what you have stick with it

[lincolnland]

3.5 gears and a trutrac.