First of all congrats on the purchase, missed this cruiser 2 times i think first time when it was being auctioned and than when a guy in h-8 was selling it. Its a nice machine but interior need a little work. u know grey and brown if u know what i mean and if this is the same rig.
About the Diff lockers well bro i myself bought one 92 auctioned 12 valve rig and converted it in to vx trim. Diff lockers were added too, got them for 75000rs after trading in the old tubes and axles. Another 10 grand to get them all serviced and put on the rig and obviously electric later on. Most of the time the motors of diffs are jammed and might need replacing which will be 3500rs a piece. overall u are looking at one lac.
Word of advice dont trade in ur diff sell them seperately might fetch u more money.That way the tubes with diff will cost u somewhere around 1 lac or 110 grand(just the diff locked tubes).
If u need any info regarding upgrade to this mean machine am always there to help out. Feel free to contact. regards salman alvi.