[Captainfab]

Since your truck is a 1/2 ton and you don't plan on removing the engine, I would just swap the control arms, and everything outward from there. As always I do recommend upgrading to the larger diameter lower control arm shaft U-bolts. This will require drilling out the holes in the crossmember.

As for the steering, you will of course need the steering box with the pitman arm. And I recommend using the newer steering linkage, complete from spindle to spindle. This will require drilling holes for the newer style idler arm. I just take measurements from the donor truck, to locate the idler arm on the early frame and drill the holes. You will also need a steering box adapter plate. I sell those along with the tube and flange, which makes the installation a little easier, You can also use the lower steering column shaft from the donor if you like. And don't forget you will need a power steeering pump, mounting brackets, pulleys and hoses. The pulleys and brackets will need to be specific to the engine you are using. In your case, the GMC V6, which can be hard to find. You might consider fabbing some, or having someone do it for you if you don't have the means.

If upgrading to power brakes also, you can use the booster and master from the donor if you like. I also sell booster brackets, that work with a few specific boosters that are commonly available. These are a direct bolt onto your firewall.

I don't know for certain on the '87 G20 parts, but I do know that a '85 G20 would work. I would think the '87 would be the same, but I would verify before purchasing. Maybe do a part interchange at an auto parts store, to see. If you are planning on the aftermarket 6 lug conversion rotors, then you will need the spindles for the 1.250 thick rotors.