One sort of tell tail way to know is the height of the mounting surface for the fuel pump/oil fill stand on the intake manifold. For example if you look at the first two pictures attached of a mid/late 35 & a 36 intake where the fuel pump stand mounts, its a lower rise than the last picture of a 34 & early 35 intake. Your rod, I believe, should be the longer 8-3/4ish rod not the 7-3/4ish.