How to turn my 1980 ford f150 stepside into a 4wd?

How to turn my 1980 ford f150 stepside into a 4wd? - 1

Spend lots of money is the only way.
Cheaper to buy a good used truck than spend money converting this one to a 4 wheel drive

Easiest/best way is to trade it for one.
There's just so much different between the two.
I-beam axles, rotors, springs, perches, transmission and transfer case, driveshafts…

The only parts that are really the same are the engine (and related components), frame and body.

You sell it and buy one with 4WD. That will be a lot cheaper and easier than trying to convert what you have.

Spend a but load of cash and time making the conversion. Otherwise, simply trade the vehicle for one which has the options and features you want.

Even the frame is different…

The reality is that you can't. To convert a 2WD to a 4WD would cost more than buying the 4WD.