I know this question has been asked a thousand times, but I ran into a snag on my second swap... The mounts I have are for a '68 318 B-body, and it is going into a '71 E-body. The PASSENGER side holes are effectively backwards. The block has two holes on the front set and a single upper rear, but the mount has one upper hole on the front and two on the rear. See pic below. The ones on my '68 Charger swap (forgot the application of the mount donor) had 4 holes on the passenger side so I could use all three on the block.