If you keep the original springs you can use the adapter spring Pearch .not sure if the newer rear end has the same spot we’re the spring goes .the ones pictured are offset to put the axle in the center of the wheel well when using the original springs .
I considered using those adapter perches when I did mine. Ended up just buying a set from the farm store and drilling my own holes to move the axle back. Super cheap way to do it. I think they were $10-$20.
believe getting the axle centered in wheel well takes something like 1.75” offset in the perch. My truck had been previously converted to open driveline and I didn’t want to screw with a new driveshaft. So I opted for less when drilling the hole….i think just an inch forward.
