I know that this advice may have been more appropriate before the original hole drift but this may be helpful with the second attempt. When I installed my plate I was so concerned about the possibility of drift and alignment that I did things a bit different from the instructions. First, I built up the area on the block under the plate with a bit of JB weld and filed it down so that I had a flat area for starting the hole. Second, I found a piece of thin wall steel tubing about a 1 ½” long that fit snugly into the water pump/adaptor plate. I tapped the tubing into the water pump/adaptor plate and bolted up as per instructions. With this in place, the tubing provided a drill guide that kept things straight, centered and allowed me to use a smaller diameter drill (smaller then the tap size). I initially used a drill that just fit in the tubing. After the initial drilling, I followed up with the larger appropriate tap size drill enlarging the hole in the tubing and the block. I removed the tubing tapped the hole and was good to go with perfect alignment. Worked for me but maybe it was just dumb luck on my part. Sounds like you got the bad luck part.
