Steve is correct about partial rotation on roller and needle bearings.A few years ago ,Toyota I think, was having premature wheel bearing failure on its cars. After much investigation, they found cars shipped by rail were rocking back and forth on the rail cars during shipment.This action was causing wheel bearing failure on new cars, the bearing races were indented from the action.But some motorcycles use tapered roller bearings on the swing arm pivot with out problems, so....?
Another problem with the needle bearing conversion is line boring the spindles for the bearing installation.Many old spindle eyes are egged shaped from all the pounding over the years. This is no problem if you prees in new bushings then ream them to size.But the needle bearing shell will be distorted when pressed in. If the kit requires boring of the eyes, then this won't be a problem of course.
Old GM trucks from 41 up with the Saginaw recirculating ball steering box will steer quite well if the box and various rod ends are in good shape.Our 51 Chevy steers just fine with new front parts and a good steering box,as good as any much newer non power steering truck.
Play close attention to the tie rod and drag link ends, the stock pressed in balls are likely to be worn oblong, replace the balls or use a modern style tie rod replacement.The front beam axles may also take a "set", meaning the wheels have too much negative camber, incresing steering effort.The camber can be easily checked with the truck resting on its wheels by using a level and some blocks so the level is against the rim not the tire.Truck alignment shops have the hydraulic tools to bent beams back into specs.If its ok, set the castor around 2-4 degress with spring pad shims with the truck sitting at its normal attitude. The toe in can be accurately set with a tape measure if you are careful.
