Not sure a Locker would be practical for a street truck, limited slip/positraction is OK.
Look at your drivers door sticker to see what you have now, codes are here: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes
You may already have it, but most likely not.
You can then decide if you want to swap whole rear axle or just ring and pinion gears.
On this sticker you will also see the VIN for the vehicle, write it down.
Go to or call a Ford dealer and see how much the Cruise Control kit is and if it can be used with your VIN
Reason is some vehicle wiring harnesses can have Cruise added, some can't.
If yours can then you can hit a wrecking yard to pick up all the parts cheaper.
You need new steering wheel(with cruise buttons) and clock spring.
Servo for throttle and speed amplifier(brains)
Also the brake pedal cutoff and clutch pedal/NSS cutoff.
If yours isn't wired for it then adding a 3rd party cruise will be the best option.
Outside of the limited slip axle best bet is to keep current Ranger clean and watch the papers for similar Ranger with all the factory options you want.
Then sell yours and buy the one with all the goodies, that would be money better spent.
Once you start rewiring factory harness you can get into a bit of trouble with other systems, the newer vehicles are filled with microprocessors that are constantly monitoring status of themselves and the rest of the system.