there are left and right , the holes for the bolt through the frame perch are closer to the backer plate on driverside , . if you tru to put driver (right ) on on passenger side (left) the holes in mount will not be low enough to insert the through bolt
on the ones i got from kirbans they were both the same which doesnt surprise me because the passenger mount was always a cheaper than driverside and will fit on driverside . but it screws up the motor alaignment.
with that said after the kirban mounts failed to keep the motor inplace i put an HR poly mount on driverside and since then the motor was tilted toward passenger side so i purchased a passengerside replacement from autozone (pioneer) and had a hard time getting it in , had to notch (cut slots to the holes with a grinder) it to get the bolt to work and used a large washer on each end of the bolt , but i did accomplish what i wanted which was raise the motor on passenger side up to put the motor back to straight up and give my DP more frame clearance,
maybe there is something wrong with the mounts that pioneer is selling for passenger side , or maybe they boxed driverside into the wrong box