On the 427 cars the rods are staggered in the front, so the jacks can only go on one way.
The 289 cars have the rods straight (vertically) so they can be flipped either way.
Of course you may decide, like me, that you've scraped skin off your leg for the last time and are replacing them with overiders.
(it was either that or tying pillows on the darn things)
I haven't had the pleasure of laying my forehead open on one yet like some folks.