These are 318 brackets on a 318 engine. The first two pics are drivers side, same bracket different angles. The drivers side is the side you need to change, narrower on a 360. The pictures are the same brackets you have for the 273.
Did you see this link ^^^^^ The brackets you bought are B body brackets and won't work. Maybe you have the sides switched up. The pics I posted are correct on a 318 for a 67-72 A body. Hope this helps.