Early Ford Spindles fitting early Ford axles
There is always a cloud of misinformation floating over any discussion of early (28-48 Passenger and 28-47 Pickup) Ford front axle components, particularly the axles and spindles.
The kingpins used on 28-28 axles on passenger cars and pickups (1/4 & 1/2 ton) are the same diameter and so will fit all the axles under these specified vehicles. The differences lie in length, location of locator slot, and configuration of the top of the pin.
Any of the 28-48 Passenger and 28-47 Pickup spindles will fit any of the 28-48 Passenger and 28-47 Pickup axles, just use the kingpin set which is correct for the spindles you have. Of course most changes will be using the 37-38 spindles on earlier axles rather than the early spindles on late axles.
The 28-36 kingpins have mechanical brake rod cups on top of them. These pins can be replaced by 37-41 or 42-48 flat top kingpins by simply grinding a correct locator slot in them for the spindle being used and matching the lengths as closely as possible.
Spindles 28-31 have a knuckle on them where the steering arms bolt on similar to the much later 48-52 pickups. They have integral steering balls and use spring-loaded tie rod ends.
32-34 Spindles have steering arms as part of the spindle (2 on the left and i on the right) and use round replaceable steering balls and spring-loaded tie rod ends.
35-40 spindles have steering arms as part of the spindles (1 on each side, the RH having 2 eyes) and use conventional tapered shaft tie rods ends.
Spindles break down as follows:
28-31 Model A Passenger and Pickup
32-34 Ford Passenger and Pickup
35-36 Ford Passenger and Pickup (although there are a 35 and a 36, they are interchangeable)
37-41 Ford Passenger and Pickup
42-48 Ford Passenger and 42-47 Pickup
28-36 spindles have a longer stub axle than the 37-48 spindles and a smaller flange where the brake backing plates mount.
37-41 spindles are known as round-flange spindles.
42-48 spindles are known a square flange spindles.
Front hub and brake drum assemblies from 37-39(nowadays popularly called "wide-5"), 40-41, and 42-48 will fit directly fit all spindles from 37-48 with no change of bearings or seals required. They will fit 28-36 spindles using bearing spacers with no change in bearings or seals.
Hydraulic brake backing plates from 39-41 and 42-48 will fit all 37-48 spindles
and will fit the 28-36 spindles with centering rings and modifying the mounting holes by slotting them down to fit the smaller bolt pattern on the flanges.
Of course the later F-1 and F100 brakes, as well as the early Lincoln brakes, can be adapted to the spindles as well but there are many posts describing this change.