I used a heavy plate with appropriate holes on top and half round U-bolts under the axle when I swapped an axle with 4" tubes under my 1 ton. It's just not quite as clean looking as the factory saddle under the axle.
There are some sorts of factory upper brackets (instead of plate steel) but not sure where to suggest looking for one for 2" springs and 3.25" axle tube, that combo may not exist.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-