The original rear spring setup on a 1951 3100 1/2 ton should look like the attached photos.
The axle housing is connect to the spring seat with a rubber bushing inside.
The spring seat is U-bolted to the leaf spring.
Torque tube connection at rear of transmission prevents axle from rotating.

There is one bolt thru the stack of leafs and it is off set to the front.
The spring seat sits on top of the one bolt.
The leafs are centered under the spring seat.
Axle is centered in wheel well or fender.


Read Rear Spring Seat

The 2nd picture shows the spring seat and its u-bolts and the overload spring's u-bolts on the axle housing.
There is a stack of 10 leafs which is a 1954 1/2 ton Heavy Duty Rear Spring RPO 254E, regular equipment came with a 8 leaf stack.

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Attachments
half ton leaf spring axle mount rz.jpg (25.9 KB, 112 downloads)
Spring Seat rz.jpg (125.48 KB, 161 downloads)

1954 Chevrolet 3105 Deluxe Panel Truck
w/Factory HYDRA-MATIC