Regardless of what car it is, the bleeder (whether it's an actual ball valve, or simply a small hole with a jiggle rod in it) must always be on the highest point on the rim. Only when the rim is perfectly horizontal doesn't it make a difference -- but even the slightest tilt, however, compels the aforementioned specific placement.

This is simply because air bubbles float in liquid, and therefore they will congregate and fuse into an air pocket at the highest spot under the thermostat -- where the bleeder would let them readily escape to the top of the thermostat where they can return to the radiator and be purged through the hose to the overflow tank.