Shock angle is actually more important than some give it credit for. Shocks work the best when they are running vertical. Their effectivenss is reduced as the angle drops from vertical. 45 degrees is about the max that a shock can be run and still be effective. So if you're a bit more vertical than what the '51 run, it's not really a big deal. Might actually be better.
As far as bottoming out or hitting full extension, you would definetly know as yu would be able not only to feel it, but hear it as well. As long as you have the length of the shocks travel longer than the suspension travel, and the shock is mounted at roughly center of the travel, you should be fine.

Bill Burmeister