Skip the locking ones
I've got two of these installed on my truck & use them a few times a month for road & mountain bikes. They are easy to install & work great. My advice is to skip the locking units that sell for a little more & get the standard ones. When you do put the bikes on, just toss a cable through the frames & wheels then lock them to the tie down point in the bed. The bikes are more secure from theft that way anyway.