I have rebuilt 2 of these, my last being a block from a 2000 caravan. Regardless of the block, if it is a 6G72 you should be able to mount a pump from the Gen 1 montero with the integrated oil filer mount with no problems. Are you sure you have the correct pump? Also, this seems obvious, but have you flipped that gasket around to see if you can get the mounting holes to line up? I admittingly have made mistakes like that before... Lol. If it is a motor from a caravan, the drivers side will have a oil filter mount that must be removed to mount the motor mounts.