First off I do not know what motor gears are ?
If you learn to use Commas and Capital Letters then the title would read differently.
i.e. "Motor, Gears and Lockers”.
Now back to the new title…
EFI is the only way to go and if you get a motor, wiring harness and the computer from an early ‘90s Stang then you will have almost a bolt in.
EFI is better off rod won’t stall when on a hill like some Carb’d Engines.
The wiring harness is a drop in from a ’93 Stang, add 12 V power to the correct wire connect the wires to the fuel pump and now you should be able to fire her up.
Ford has a pamphlet for this process.
The Gears will depend on the tire size, 3.73s in my opinion will work with 30” tires but if you go to 33s or 35s then 4.30s, 4.56s or 4.88s will come into the picture.
OK the Posi in the rear and a locker in the front, good but if possible switchable lockers in both the front and the rear will get you further.
If the Posi you got is out of the Axle Housing then you will need to set it up anyway so save a little more and get another switchable locker.
Gears Ratios, the 3.73 Carrier may not be able to use 4.56/4.88 gears if you go that way, so a new Carrier (Locker) is advisable so make it a Locker.
4x4, 5sp, Std Cab, Stepside, E4 Red
4” Lift - Coil-Overs, 6” SkyJacker Leafs - No Blocks (Mistake)
31 Spline FX4 Rear Axle, 4.56s and OX Locker, Hurst Shifter w/Optional Stick and "Made by Grev" alignment adapter