292 to 250 swap

[snafu1]

Hello fello forum members. I need some help with a 1968 GMC. It had a 292 in it but threw a rod and put a nice hole in the block. I was not able to find a 292 in my area but came up with a 1970 Nova 250 motor, that was standard bore. I am having trouble getting the motor mounts to line up. I am useing the stock perches that came on the truck and I moved the passenger side perch back, into the holes already in the frame. I used the metal brackets that came with the 250 motor and installed new rubber mounts for the 250. The trouble I have I can not get the passenger side mount lined up! Is there a difference? Am I doing something wrong or do I need different perches? Please help!
Thank you,
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