For what it's worth,I used a rear end from a mid 70's Chevy 4X4 under my 57 GMC;the spring pads were about half an inch too wide,but there's enough flex in the springs and shackles to allow it to fit. The width at axle flanges is just right for the 57,it might work in your 46 too.Had to do some modifying to get the spring plates to work right since my springs are not as wide as the later ones,used the u-bolts that came with the rear end,I had to buy a fitting for the brake hose,and my 57 e-brake cables fit the newer rear end just fine. I did have to build shock mounts. Since that required welding anyway,I set them up to fit stock mid 70's Chevy truck shocks. (great selection,low prices,and parts stores keep 'em in stock) I now have a 3.08 ratio in it-works great with the Pontiac 400 engine!
Seems like GM's suspension parts are transplantable enough to enable a huge selection of possibilities.
Speed
