When I installed a few fridge in our 67 a couple of months ago, I ran into the same problem that your dealer undoubtedly noted: In the old ones, the fridge is bolted to the floor; however, the new fridge wants to be bolted/screwed in from the sides. The problem is that there just isn't anything to bolt/screw into on the sides of the cabinet of the older rig, and there's no way on the new fridge to bolt/screw downwards to the floor.
Soooooo, the solution I came up with two-fold:
1. Build a tray-like thing so that each of the feet of the new fridge are sitting in a small depression.
2. Use a strap inside the cabinet going over the top of the fridge, holding the whole unit tightly down into the depressions under the feet.
I was wondering if we'd see any movement of the fridge on our last trip, but was happy to see none whatsoever.