Rear Shock Won't Mount to Shock Mount

My car has originally a 7 1/4 rear end (72 duster) but I replaced it with a shortened ford 8.8 rear end. I bought the 8 3/4 rear shock mounts from Mancini, enlarged the holes a little bit so that the 3.25 wide u bolts would fit over the axle housing and into the shock mounts.

When I tried to actually mount the shock to the shock mount, it wont fit. The angle at what the shock is at seems to be too extreme for the shock to slide onto it. I have tried jacking on the shock to try to get a more straight on angle but still no luck.

Anyone have an secrets on how to mount rear shocks? Or am I doing something wrong?

Photos are somewhat demonstrative (the u bolts aren't all the way tight). the u bolts were actually tight when I attempted to mount the shocks.

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